Detecting design time?

From: Robert J Baker (korax1214_at_mailandnews.co.uk)
Date: 06/24/04 

Date: 24 Jun 2004 12:57:51 -0700

I've now got updated Help files and they're good; however, there still
seems to be at least one thing lacking.

How does a property-editor routine detect whether it's running at
design time, or at run time? I'm sure there's a way (all that's
needed is a Boolean function which returns True at design time and
False at run time, or vice versa, whichever is more convenient to
implement), and I'd like the write procedure for one of my component
properties to react to an out-of-range value with a dialog box at
design time or an exception at run time; but I can't find anything
relevant in the help files (I must admit that I haven't ploughed
through the *entire* Component Writers' Guide -- although I'm grateful
that this at last explains how to construct dialog boxes)...