Coding out and about without my libraries drive and hit that old, old, old bug of user controls not making it easy to tell you when you're in Designmode if you nest subclassed UCs. Felt like a noob fool, had to waste time running through all of the forum posts of hacks that still don't work.. till I found this one. It's not mine but it's better than mine in that it works (for me) across the nesting scenarios even when called from a grandchild control. Now I'm glad I forgot my drive :).
The code is in an Anonymous comment, in case that page goes away, I put it here.
Why does the simple DesignMode feature that was spot-on in the VB5/6 era still elude the VS team after ten years of .Net?