The resize event doesn't have the ability to change the
properties of a popup window while the creationComplete event can.
I would think that if the creationComplete event can access it, the
resize event should also be able to. This doesn't work in Flex 2
either, although it doesn't generate an error. Tried it also in
Flex 3 without AIR, didn't work.
A RESIZE event usualy occurs before CREATION_COMPLETE as the
components in the application are being layed out, so helpWindow
hasn't been created yet. The INITIALIZE handler runs before RESIZE
so that might be better for you.