How to transfer variables from Excel2008 to AppleScript using a "function call"

Hi folks,

I have a self written function in VBA which gets 2 variables as input
makes different calculations and returns one value back.

In EXCEL I called this VBA function simply  by typing 
=Calculation (A1, C3) + Calculation(D27, G58) + ....

Now I do not know how to handle this in AplleScript :(

How can I call this script from Excel and how can I transfer the 2 input
variables ant the output variable back into Excel?

Thanks for help
Manfred