SysTabControl32 and Background image

[errbor]

How can i access to c1005Che chexbox state from main dialog in dlg_multipage_with_tab_control3 example above?

for example if i add button in main dialog and use

Code:

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,case <button id>
,,if IsDlgButtonChecked(hDlg0 1005)
,,,out "1"
,,else
,,,out "0"

it doesnt seem to work