A function to only allow numeric input in a textbox

[mshmyob]

Here is a way to limit user input in a textbox to only numeric characters.

I have created a function and I put mine in a Class module that holds my custom functions. The function is called from the KEYPRESS event of any textbox control where you want to limit to numeric input.

The only parameter you may wish to change is the last parameter which determines the number of digits to the right of the decimal place. This sample code limits the input to 2 decimal places.

Code for KEYPRESS event

Dim myTextBox As TextBox
myTextBox = Me.ActiveControl
If myMiscClass.myNumOnly(e.KeyChar, Me.ActiveControl.Text, myTextBox.SelectionStart, 2) = True Then
        e.Handled = True
Else
        e.Handled = False
 End If
If e.KeyChar = Chr(13) Then GetNextControl(Me.ActiveControl, True).Focus() 'Enter key moves to next control
 

Code for Function (I put this in it's own class module (so I only need it once) but you may put it in your form module if you wish.)

'*****************************************************
' myNumOnly()
' Purpose: Limits textbox input to numeric only
' Inputs:   strKeyPress, key pressed
'           strText, current text in textbox
'           intPosition, current cursor position in textbox
'           intDecimal, number of decimal places required
'       ' Returns: False/True - discard keystroke/valid key
'*****************************************************
Shared Function myNumOnly(ByVal strKeyPress As String, ByVal strText As String, ByVal intPosition As Integer, ByVal intDecimal As Integer) As Boolean
 
Dim dot As Integer, ch As String
 
If Not Char.IsDigit(strKeyPress) Then myNumOnly = True
If strKeyPress = "-" And intPosition = 0 Then myNumOnly = False 'allow negative number
If strKeyPress = "." And strText.IndexOf(".") = -1 Then myNumOnly = False 'allow single decimal point
dot = strText.IndexOf(".")
If dot > -1 Then 'limit to set decimal places
       ch = strText.Substring(dot + 1)
       If ch.Length > (intDecimal - 1) Then myNumOnly = True
End If
If strKeyPress = Chr(8) Then myNumOnly = False 'allow Backspace
Return myNumOnly
End Function
 

Feel free to ask any questions.

cheers,

[yarbrough40]

Thanks for this! I have written it in a notepad for posterity.