The syntax I'm using has 2 modifications. First, I had to explicitly skip processing any bars from the VFP System menu because issuing Set Mark of Bar n to .f. on them caused an error. Second, if you do Set Mark false on all custom bars except the active one while you're looping through them, you only need to call the method once--from the Activate(). Both of these issues are neatly handled in a Case statement.

I'm really pleased with the way this works. It's certainly worth the frustration of yesterday <g>. Even if the user instantiates multiple instances of the form displaying the same data and then closes some, the menu mark is self-correcting. Pretty impressive.

Thanks for your help!