Input first character of string

[MyEarth]

Hello,

I want to allow a character, like !, only is in the first position of the input like:

!abc

The problems is how...If i use StringLeft($Input, 1 ) work only if the string is empty because if i have:

abc

And i move the caret at the first position, like.

|abc

And i try to write not work bacuse the StringLeft($Input, 1) = c

I have think something like the char at the left of the caret but i don't know if possible. Any suggestion are welcome. Thank you

EDIT: Or maybe some RegExp for check if ! is the first character, if not replace it with ""

Edited October 21, 2014 by MyEarth

[funkey]

#include "RestrictControlRegExp.au3"

Opt("GUIOnEventMode", 1)

_RegEx_RestrictControl_setup (20) ; prepare for up to 20 Controls to restrict

GUICreate("Test")
GUISetOnEvent(-3, "_quit")
$inp = GUICtrlCreateInput("", 10, 200, 100, 20)
_RegEx_RestrictControl_add ($inp, "\A[!]", "!abc")

GUISetState()

While 1
    Sleep(10)
WEnd


Func _quit()
    Exit
EndFunc   ;==>_quit

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[MyEarth]

Thanks