Thanks for the reply, But I've already solve this problem.
I just found out that I put
oMouseOverObject = sys(1270)
On the 1st line of textbox.lostfocus, before applying to open modal form.
So when I put LOCAL oMouseOverObject on the top line, it works good.
But anyway, thanks for reply.
Senna Dwipayana
Being good is better
Being better is a bless