[Dev-C++] problem of modeless(modal) dialog box

[Jessica C. <jes...@gm...>]

i used CreateDialog to create a dialog box.

CreateDialog can create dialog box without disturbing the applications
running behind.

but the problem is: after i push a button to trigger a dialog box opened, i
can still push that button to trigger the dialog box opened again.  but what
i want to get is just 1 dialog box.  i mean, after the dialog box is opened,
then i cannot trigger the same dialog box by clicking the same button.

i think the problem is from modeless/modal concept.  what shall i solve this
problem?