Hide ' X ' box in a dialog

[C++ Programming]

Hi,
I want to hide 'X'-box or Close-box (which we can find at the Top-right corner of a Dialogbox).
Can any one please help me ,what should be the code to hide this box in MFC.
please let me know as soon as possible.

Thanks in advance http://www.barakasoft.com/script/Forums/Images/smiley_smile.gif