QueryInterface Failed

[Francis B.]

Hi!
In one of my base classes, I have a function which receive a callback from
another application. In this function, I would like to access
Excel.Application object but I receive an exception: QueryInterface for
interface Excel._Application failed.
If my class were inherited from Windows.Forms, I could use BeginInvoke
function. So I would like to know a way to access Excel.Application object
in my callback function.

Build with C# for Excel Object 9.0 (Excel 2000).

Thanks in advance!