Banning Specific Characters In A Cell []

I need to ensure that the client names entered don't contain certain banned characters (* / : ? [ ]) as the name entered will be used later to create a file name. This is what I have written (in the Worksheet_Change event):

If Target.Column = 1 Then
If Target.Value 0 And Target.Value "" Then
Dim intFound as Integer, ranFound as Range, i as Integer
Application.EnableEvents = False
Application.ScreenUpdating = False
intFound = 0
For i = 42 To 93
Set ranFound = Target.Find(Chr$(i), LookIn:=xlValues, lookat:=xlPart)
If Not ranFound Is Nothing Then
Select Case i..........................

Which is all very well, but it treats character 42 (*) and character 63 (?) as wildcards and even good client names are rejected. How do I search the entry to find if there is an actual * or ? in the target.value?