Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

    Dim itemName As String = txtItem.Text
    Dim qty As Double = CDbl(txtQTY.Text)
    Dim price As Double = CDbl(txtPrice.Text)
    Dim Total As Double = price * qty

    txtTotal.Text = Convert.ToString(Total)

    Dim row As Integer = grdNewInvoice.Rows.Count

    Dim data As TextBox() = New TextBox() {txtItem, txtQTY, txtPrice, txtTotal}
    grdNewInvoice.Rows.Add()

    For i As Integer = 0 To data.Length - 1
        grdNewInvoice(i, row).Value = data(0)

    Next


End Sub

'grdNewInvoice.Rows(0).Cells(0).Value = itemName
    'grdNewInvoice.Rows(0).Cells(1).Value = qty
    'grdNewInvoice.Rows(0).Cells(2).Value = price
    'grdNewInvoice.Rows(0).Cells(3).Value = Total

Dim row As Integer = grdNewInvoice.Rows.Count

Dim data As New List(Of String())
data.Add({txtItem.Text, txtQTY.Text, txtPrice.Text, txtTotal.Text})
data.Add({"Item2", "qtr2", "price2", "total2"})
data.Add({"Item3", "qty3", "price3", "total3"})

For i As Integer = 0 To data.Count - 1
    grdNewInvoice.Rows.Add(data(i))
Next