I have a workbook (a) that create another workbook(b).
I will need the new workbook (b) to use a function (in the excel sheet - not
vba) that is user-defined in the code of the original workbook (a).

I can do it if I add a reference in (b) to (a) - but
1) is there another way, simpler (with no need to add reference something
like =a!Functionfroma (x,y) ?
2) how can I do it programaticaly (adding a reference) when creating
workbook b?

Any idea.
Many thanks,
Dan