Just a hint :
Local $sInput = "a...az019bc.-_"
If StringRegExp($sInput, "[^a-z0-9._-]") Then
ConsoleWrite("found forbidden chars" & @CRLF)
Else
ConsoleWrite("Input OK" & @CRLF)
EndIf
EDIT : @xXKlaskpffXx
If you want to check the characters while typing, have a look at e.g. :
preventing-invalid-characters-from-being-entered-into-an-input-control