Hasta La Motion!

I have another question about python in nuke:
when nuke executing my script the command nuke.frame(x) don’t work properly.

track() calls for "track to the next frame" button in Tracker
proverka() cheks results of tracker and in some cases should forces tracker to start track from the begining, but nuke.frame(x) doesn’t work. if i insert "print nuke.frame()" after "nuke.frame(x)" he will print the correct frame number, but will track forward ignoring this command 🙂
i think time.sleep() after nuke.frame(x) could solve this problem but for some reasons nuke calculates summ of time.sleep() and gives result after some seconds 🙂
may be there’s any way to force scipt to wait until viewer refreshes or some other way to make it pause. does anybody know?
sorry for my english, but i can’t find the solution by myself 🙂