Closing first dialog box while second is still running

[C++ Programming]

Hi all,

I have made a Dialog based application in vc 2008. In my application i am opening second dialog box using DoModal() on a button click event of first dialog box. In second dialog box i am starting a worker thread in my OnInitDialog() function.My problem is while my second dialog box is still doing some work, first dialog box can be closed in the back that is it is active.

Please help me in this

Thanks in advance