How to update another text box while typing in access 2007 form?

Question

I have a few text boxes which have to be filled with numeric values from 0 to 100. Below them there is another text box which stands for a total (the sum of the values from the text boxes above). How can I update the sum text box while typing in any of the other text boxes above?

Answer 1

This is problematic due to the asinine requirement in Access that you have to set focus to text areas before you can get their value. I would recommend you change your design so that the text field is updated in response to a button click instead of on change.

If you want to go the update-on-change route, you would attach change events to each of the addend text fields. The event handlers would need to save the caret position/selection length, update the sum in the output text field, and restore the caret position. You need to save/restore the caret position because this is lost when the focus changes.

Here's an example for two text fields (txt1 and txt2). The output field is named txtOutput.

Private Sub txt1_Change()
    Dim caret_position As Variant

    caret_position = Array(txt1.SelStart, txt1.SelLength)

    UpdateSum

    txt1.SetFocus
    txt1.SelStart = caret_position(0)
    txt1.SelLength = caret_position(1)
End Sub

Private Sub txt2_Change()
    Dim caret_position As Variant

    caret_position = Array(txt2.SelStart, txt2.SelLength)

    UpdateSum

    txt2.SetFocus
    txt2.SelStart = caret_position(0)
    txt2.SelLength = caret_position(1)
End Sub

Private Sub UpdateSum()
    Dim sum As Variant
    sum = CDec(0)

    txt1.SetFocus
    If IsNumeric(txt1.Text) Then
        sum = sum + CDec(txt1.Text)
    End If

    txt2.SetFocus
    If IsNumeric(txt2.Text) Then
        sum = sum + CDec(txt2.Text)
    End If

    txtOutput.SetFocus
    txtOutput.Text = sum
End Sub