Any ideas on how to fix this or make it work correctly?

I have 2 workbooks.

1 is the workbook that counts many worksheets

the other is a workbook with 1 worksheet.

I want to move the workbook that contains 1 worksheet into the other workbook which has alot of worksheets, but when i do this it seems to trash the workbook that contains many sheets, in that i cannot access any properties of the workbook instance, it gives me COMException, and thats it.

Before I move it, its fine but after, it gives me COMException when accessing the application property or any other properties but DOES succeed in moving....