Dialog box - limiting resizing to one direction (x or y)

I'm resizing dialog box (by setting attributes to DIALOGATTR_DEFAULT |
DIALOGATTR_GROWABLE | DIALOGATTR_MOTIONTOITEMS)
and then some code in the hook function. Is there an easy way to limit
dialog box resizing to width (or height) ? In some circumstances I want to
allow
the resizing in one direction only.

Any suggestions ?

Thank you.

Jarek