Draging a form after setting FormBorderStyle to None

Question

I have a windows form .
          
             I have set FormBorderStyle to None.

and given my own image borders. Now the problem is that

I can'nt drag the form.

What I have to do to make it dragable ?

I mean I will be having one image... like form

header . User should be able to drag form from there like we normally drag our

windows forms.

plz do help if possible.

thank you