ok, check this out;

To open a dialog box from another dialog box:

right click on the dailog folder in the resource view and select 'add resource'. add a dialog resource that inherets from CDialog;
when the dialog templete opens up, double click on it to attach a class. give it a name (subBox in my example), and make sure that it inherets from CDialog;

include the header file for the child dialog box in the parent dialog box code. i.e. add #include "subBox.h" to Boxdlg.cpp.

then you open the dialog box when button 1 is clicked like this:
Code:
void CBoxDlg::OnBnClickedButton1()
{
	subBox sBox;
	sBox.DoModal();
}
subBox is the class that describes your child box, and sBox is an instance of that class (the child dialog box object).

this should work for you, it worked in my example. If it still won't open, post up the error messages;

C ya;