Finding out the page calling the code

[liunx]

I have a user control which can be called by two different pages. page1.aspx and page2.aspx

if page1.aspx calls button 1 will bring to page3.aspx
if page2.aspx calls button 1 will bring to page4.aspx

is there a way of doing this. i assume it finding what the parent url is

thanks

franksorted