Wrong instance of Workbook instance activating on dialog display

[crewaustin66]

We have an application that works fine up to MS Excel 2010. M$ changed from an multiple-document interface to a single-document interface in 2013. Now the behavior of my application has changed. Each workbook now opens a completely separate instance of Excel (SDI). That's fine and all works well accept for one thing. If I have two workbooks open (A&B) and A is active, instance A tries to open a dialog but it forces a switch over to instance B. Right on the formName.Show the swap happens. I can't figure it out.

Thoughts from the group?

Thanks,
Crew