Try to declare result variable in your main program, e.g.

local Result
Result = 'N'

do myForm to Result

>Hello All
>
>This is very simple, but yet not working
>
>I have this in my main program

>SET TALK OFF
>DO FORM frmsplash
>DO FORM mylogon TO result
>IF result="Y"
>	DO FORM mainform
>	READ events
>ELSE
>	WAIT WINDOW "not logged in"
>	QUIT
>ENDIF
>

>sample code in mylogon form
>
>mylogon form had username and password
>if sucessfull login
>thisform.aa="Y"
>else
>thisform.aa="N"
>
>mylogon form is modal and in unload event
>return thisform.aa
>
>This works fine within VFP 9 but when compiled into a exe I get a message Variable Result in not Found.
>
>Thanks for any input