在visual basic中计算程序

Question

I trying to make program in visual basic in Text Changed event that when enter value the text box the program will store that value and when delete that value and enter new value it will use the first value and Compares with the new value if the new value > from the first value Decreases the new value from the first value (new value-first value) and if the new value < from the first value it will Decreases the first value from new value (first value - new value) and the The result another text box

Dim f As String
Private Sub TextBox2_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.TextChanged
    If TextBox2.Text > f Then
        TextBox18.Text = TextBox2.Text - f
        f = (TextBox2.Text)
    End If

I make this code it work but when the new value is (10) or Larger its not working

Answer 1

Try the following:

Dim f As String
Private Sub TextBox2_Leave(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles TextBox2.Leave
If not string.isnullOrEmpty(TextBox2.Text) Then
If CDbl(TextBox2.Text) > CDbl(f) Then
    TextBox18.Text = CStr(CDbl(TextBox2.Text) - CDbl(f))
    f = TextBox2.Text
End If
End If
End Sub