multipage dialog, execute code when on certain page number

[r0n]

1)
I have a dialog that contains 2 pages, when I click a button called "generate" from first page it goes to the second page (page 1).

Question: How can I execute code on page 1 (second page))?
The code may only run specifically when user is on page 1 (second page).

In a one page-dialogbox (normal, none-multipage) I would simply put the code under "WM_INITDIALOG" which worked perfectly.

2)
Question: And how can I output this in the output window:

Code:

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page: #

(#= current pagenumber of multipage dialogbox).