Thank you both for very helpful suggestions.
The script is for my own use. And Phil's code works perfectly ok for my purposes.

The "ANIMATIONPALETTE.Show" does appear to disable the redraws on the window. But, as Phil suggests, it is not a suitable safe method for general Users. Without loads of additional error trapping etc. If the script fails; the AnimationPalette could appear visible, but remain inoperable (requring the User to close and reopen the palette).

Interestingly, when I use the "Import" menu in Poser, the Library window becomes disabled; but also looks disabled (greyed out) as well.

But I am happy now.