Public Class Form1
    Dim Num1a, Num1b, Num2a, Num2b As Decimal
    Dim Result As Decimal
    Private Sub btnCalc_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCalc.Click
        Try
            IsNumeric(txtNum1a.Text)
            IsNumeric(txtNum1b.Text)
            IsNumeric(txtNum2a.Text)
            IsNumeric(txtNum2b.Text)
            Num1a = CDec(txtNum1a.Text)
            Num1b = CDec(txtNum1b.Text)
            Num2a = CDec(txtNum2a.Text)
            Num2b = CDec(txtNum2b.Text)
            Calculate(txtNum1a.Text, txtNum1b.Text, txtNum2a.Text, txtNum2b.Text)
        Catch Juevos As DivideByZeroException
            MsgBox("Do not divide by zero!")
        Catch ex As Exception
            MsgBox("please enter numbers.")
        End Try

        lblResult.Text = Result.ToString("N2")
    End Sub
    Private Function Calculate(ByVal num1a As Decimal, ByVal num1b As Decimal, ByVal num2a As Decimal, ByVal num2b As Decimal, ByRef Result As Decimal) As Decimal
        Select Case Result
            Case radAdd.Checked 'Plus
                Result = ((num1a / num1b) + (num2a / num2b))
            Case radSub.Checked 'Minus
                Result = ((num1a / num1b) - (num2a / num2b))
            Case radMult.Checked 'Multiply
                Result = ((num1a / num1b) * (num2a / num2b))
            Case radDiv.Checked 'Divide
                Result = ((num1a / num1b) / (num2a / num2b))
        End Select
        Return Result
    End Function

End Class



what works


Public Class Form1
    Dim decnum As Decimal
    Dim decdeno As Decimal
    Dim decsum As Decimal
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btndongs.Click
        Dim blnnumeratorvalid, blndenomvalid As Boolean
        blnnumeratorvalid = validatenum(txtnum1.Text, decnum)
        blndenomvalid = validatenum(txtnum2.Text, decdeno)
        If blnnumeratorvalid And blndenomvalid Then
            decsum = calcnyukka(decnum, decdeno)
            lblans.Text = decsum.ToString("n3")
        End If
    End Sub
    Private Function validatenum(ByVal strnum As String, ByRef decnum As Decimal) As Boolean
        Dim blnNumbervalid As Decimal
        Try
            decnum = CDec(strnum)
            blnNumbervalid = True
        Catch ex As FormatException
            MsgBox("amagad wrong form use numbars", , "validation error")
            blnNumbervalid = False
        Catch bob As Exception
            MsgBox("amagaad something wrong111. " & bob.Message, , "Look-at-dat-error")
            blnNumbervalid = False
        End Try
        Return blnNumbervalid
    End Function
    Private Function calcnyukka(ByVal decnum1 As Decimal, ByVal decnum2 As Decimal) As Decimal
        Dim decsum As Decimal
        Try
            decsum = decnum1 / decnum2
        Catch zero As DivideByZeroException
            MsgBox("fffffff", , "fuhhh?")
        Catch lolololol As OverflowException
            MsgBox("too oooo many numbers", , "too smaaaallarge")
        Catch teehee As Exception
            MsgBox("derp error. " & teehee.Message, , "yeppers")
        End Try
        Return decsum
    End Function

End Class