Close a model dialog box by custom button

Hello Experts,

I have a requirement where we are calling a subscreen from a normal screen and the in that subscreen we are calling a model dialog box.

I have created one custom button in that model dialog box i,e CANCEL.We are calling model dialog box from subscreen.

Once user see the model dialog box and want to close it,he will press close button,in that case we want to user back in the subscreen and the model dialog box should be closed.

Can u please help me how to do this.

Thanks

Mahesh