Problem with UI dialog

Hi all,
Due to limitations in Photoshop object model I need to automate some operations in non-standard way
One of them concerns to printing – I need to invoke Print dialog, select checkbox Labels, set Copies to 2 etc
Opening Print window successed, but then…

tell application "System Events"
	tell process "Adobe Photoshop CS3"
		set p to (first window whose name contains "print")-- tagging OK
		set value of checkbox "Labels" of p to 1-- if box unchecked (by default) this value =0, not false
		keystroke return--because Print button active it will emulate pressing on it
	end tell
end tell

But nothing happens and Script Debugger offers to stop script running – I think because of keystroke directed to script debugger window, not photoshop. What’s wrong?