Hi Mr. Reza
I am using the same function in the my function library (arfunc.prg) in following way

FUNCTION SetKeyboard(lcKeyboardCode)
	IF VARTYPE(lcKeyboardCode)!='C'
		RETURN
	ENDIF
	IF EMPTY(lcKeyboardCode)
		RETURN
	ENDIF 
	LOCAL pwszKLID 
	pwszKLID = SPACE(8)
	DECLARE INTEGER GetKeyboardLayoutName IN user32.DLL STRING @pwszKLID
	GetKeyboardLayoutName(@pwszKLID)
	DECLARE INTEGER ActivateKeyboardLayout IN user32.DLL INTEGER HKL , INTEGER flags
	IF ATC(lcKeyboardCode,pwszKLID) = 0
		ActivateKeyboardLayout(1,0)
	ENDIF
RETURN

To use it in the application

SET PROCEDURE TO arfunc.prg additive

setkeyboard('401') && for Arabic keyboard
setkeyboard('409') && for English keyboad

With best regards,
Zaheer