macro or event when excel gets focus

Is there a macro or event I can trigger off when Excel gets focus from another application?开发者_如何学Go

My Excel workbook interacts with another application via COM. The user selects an item in a tree control in the other application and when they return to the Excel workbook, I want to update some controls with the values of the items selected in the other application.

I can get the data OK (and I do it on startup of the Workbook via Auto_Open) and populate the Excel controls. My problem is that I can't figure out the macro or event that gets triggered when the Excel Application gets focus back. (If there is one)

TIA, Paolo

---

Subclassing may be the best way to go.

This post on the Mr Excel Forum may give you the information you need to get it working (see post number 6 by Jaafar Tribak).