how to return to an OLE workbook when ActiveWorkbook is Nothing

[bmurphy]

I have an excel workbook object embedded in another application, in
this case MathCad.

When I run a macro in an excel addin of mine, the macro goes off to
other workbook files and then needs to get back to the embedded
workbook. But that embedded workbook doesn't seem to be in the
collection of open workbooks in excel.

So is there a way I can get from my macro back to the embedded
workbook from which it was called?

Thanks,

Brian Murphy
Austin, Texas