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'String Manipulation - How to check if a string contains only Alpha Numeric Characters
Option Explicit
 
Public Function IsAlphaNumeric(sExpression As String) As Boolean
'Returns True if all characters in a string are alphabetical or numeric
'Returns False otherwise or for empty string
    Dim sTemp As String
    Dim iLen As Integer
    Dim iCount As Integer
    Dim sChar As String
 
    sTemp = sExpression
    iLen = Len(sTemp)
    If iLen > 0 Then
        For iCount = 1 To iLen
            sChar = Mid(sTemp, iCount, 1)
            If Not sChar Like "[0-9A-Za-z]" Then Exit Function
        Next
        IsAlphaNumeric = True
    End If
End Function