nsDialogs::OnClick for resource added button

I've used a resource editor to add a button to the main dialog. I'm trying to add a click event to it, but to no avail.

I've created the button as follows (in the the modern_headerbmp.exe):

PUSHBUTTON "", 2008, 8, 201, 50, 14

and I'm trying to add the click event using this NSIS code:

GetDlgItem $BUTTON $HWNDPARENT 2008
GetFunctionAddress $0 OnClick
nsDialogs::OnClick /NOUNLOAD $BUTTON $0

Is there a better way to do this?

Essential I want this button to go to a custom "Options" page. And when the options page is being shown, I want the button to go back to the first page.

So there are 4 pages total. 1. The first page, 2. the options page, 3. the installation page, 4. the finish page.

This button should toggle between the 1st and 2nd page, and disappear for the last two pages.

Would I be better off just overriding the "Back" button?