On 5 Jan., 20:56, xtriant wrote:
On 5 Jan., 20:38, "Harald Staff" wrote:

What AB said; a cell function can not write to remote cells.

So you are confusing methods and languages. Whether this is VBA or VB *or
VB.NET or C# makes no difference, you simply can not do this with a cell
function. But you can do it with what VB/VBA knows as a Sub, in a xla or
xlam addin, or a COM addin, no matter which language it's written in.

HTH. Best wishes Harald

Unfortunately, I still don't know how to proceed. I guess, I need to
learn some basics on xll-Addins in order to see how I can build my
solution which the user just needs to add and then access the
"testfunction" as described above. If anyone has a link/suggestion how
I can learn more in this area, I'd be very grateful.

Thanks to all for the answers,
I consider the thread closed.