Below is the macro code but it is working for a single cell.I want it for entire sheet.
Public Function IsSpecial(s As String) As Long
Dim L As Long, LL As Long
Dim sCh As String
IsSpecial = 0
For L = 1 To Len(s)
sCh = Mid(s, L, 1)
If sCh Like "[0-9a-zA-Z]" Or sCh = "_" Then
Else
IsSpecial = 1
Exit Function
End If
Next L
End Function