Public Class frmRevenue
    'array holding strings that are destined to be the labels of the textboxes
    'that are created on form load. i use the number of the quarter as the
    'hotkey for each textbox. last string is for yearly revenue label
    Private a_sQuarters() As String = {"Quarter &1 Revenue", "Quarter &2 Revenue", _
                                       "Quarter &3 Revenue", "Quarter &4 Revenue", _
                                       "Yearly Revenue"}
    'array to be used to hold the values of the individual
    'quarters
    Private a_dQuarters(_iQuarterCnt) As Decimal
    Private _iQuarterCnt As Integer = a_sQuarters.GetUpperBound(0)
    Private txtQuarters(_iQuarterCnt) As TextBox
    Private lblQuarters(_iQuarterCnt) As Label
    Private txtRevenueDisplay As TextBox
    'Private lblRevenueDisplay As Label


    Private Function IsValidRevenue(ByVal i As Integer, _
                                    ByRef dRevenueQuarterly As Decimal) As Boolean
        'quarterly revenue minimum and maximum constants
        Const c_dRevenueQuarterlyMin As Decimal = 100000D
        Const c_dRevenueQuarterlyMax As Decimal = 10000000D
        'error message. includes current values of the min/max constants.
        Dim ErrorMsg As String = String.Format("Please enter an amount between {0:c} and {1:c}!", _
                                 c_dRevenueQuarterlyMin, c_dRevenueQuarterlyMax)
        'making sure it isn't the wrong type of data and is within the
        'acceptable range
        If Decimal.TryParse(txtQuarters(i).Text, dRevenueQuarterly) Then
            If dRevenueQuarterly >= c_dRevenueQuarterlyMin AndAlso _
               dRevenueQuarterly <= c_dRevenueQuarterlyMax Then
                Return True
            End If
        End If
        'if any of the data is the wrong type or outside the bounds of the
        'constants, an error message is shown, the first offending textbox
        'is focused on, and the contained text is 'selected'
        MessageBox.Show(ErrorMsg)
        txtQuarters(i).Focus()
        txtQuarters(i).SelectAll()
        Return False

    End Function

    Private Sub frmRevenue_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'constructs most of the form controls at runtime
        Dim x, y As Integer
        'for next loop that constructs the textboxes and labels. the amount
        'of iterations is determined by the size of the Quarters array
        For i As Integer = 0 To _iQuarterCnt
            'creates the label(s)
            lblQuarters(i) = New Label
            'positions, fills with data, and sizes the labels
            With lblQuarters(i)
                x = 30
                y += 30
                .Location = New Point(x, y)
                .Text = a_sQuarters(i)
                .AutoSize = True
            End With
            'adds label to the form
            Controls.Add(lblQuarters(i))
            'creates the textbox(es)
            txtQuarters(i) = New TextBox
            'positions the textbox(es)
            With txtQuarters(i)
                x += 115
                .Location = New Point(x, y)
                '.TabIndex = i
            End With
            If i = _iQuarterCnt Then
                With txtQuarters(i)
                    .Name = "txtRevenueDisplay"
                    .Enabled = False
                End With
            End If
            'adds textbox to the form
            Controls.Add(txtQuarters(i))
            'ties the created textboxes to the _KeyPress
            'event handler
            AddHandler txtQuarters(i).KeyPress, _
                       AddressOf txtQuarters_KeyPress
            'Me.Height = y + 200
            'txtRevenueDisplay.Enabled = False

        Next
        ' I was trying to get the form to draw both the yearly
        ' revenue label and textbox as well. For some reason,
        ' they will not display. And since I messed with this
        ' part of the code, the Me.Height seems to have no effect.
        ' I had used a bit of trial and error to set it to the
        ' right size, but now it doesn't seem to do anything!
        'lblRevenueDisplay = New Label
        'With lblRevenueDisplay
        '    x = 30
        '    y += 30
        '    .Location = New Point(x, y)
        '    .Text = "Yearly Revenue"
        '    .AutoSize = True
        'End With

        'Controls.Add(lblRevenueDisplay)

        'txtRevenueDisplay = New TextBox
        'With txtRevenueDisplay
        '    .ReadOnly = True
        'End With

        'Controls.Add(txtRevenueDisplay)



    End Sub

    Private Function SumArray(ByVal a_sum() As Decimal) As Decimal
        Dim sum As Decimal
        'array containing quarterly revenue is passed to this function,
        'which uses a for loop to add all the values together, and then
        'returns that value as a decimal
        For i As Integer = 0 To a_sum.GetUpperBound(0)
            sum += a_sum(i)
        Next
        Return sum
    End Function

    Private Sub txtQuarters_KeyPress(ByVal sender As Object, ByVal e As KeyPressEventArgs)
        'Allow only numbers, decimals or backspaces. This was taken
        'from Demo 3: Daily Temperature
        Select Case e.KeyChar
            Case "0"c To "9"c, "."c, ControlChars.Back
            Case Else
                Beep()
                e.Handled = True
        End Select
    End Sub

    Private Sub btnCalc_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalc.Click

        Dim decQuarterlyRevenue(_iQuarterCnt) As Decimal
        Dim i As Integer = 0
        'do loop that validates all data contained in the textboxes. if all are
        'determined to contain valid data, SumArray is called, calculating the
        'necessary equation, and finally displaying it.
        Do While i < _iQuarterCnt AndAlso _
                        IsValidRevenue(i, decQuarterlyRevenue(i))
            i += 1
            If i = _iQuarterCnt Then
                txtRevenueDisplay.Text = Me.SumArray(decQuarterlyRevenue).ToString("c")
            End If
        Loop

    End Sub

    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click
        For i As Integer = 0 To (_iQuarterCnt - 1)
            With txtQuarters(i)
                .Clear()
            End With
        Next
        txtRevenueDisplay.Clear()
        txtQuarters(0).Focus()
    End Sub
End Class