INDEX as an alternative for INDIRECT

I have the code working, apart from 1 little thing that I can't figure out

During the code I determine the name of the current worksheet
(The target worksheet in the source file has the same name).

When I keep the mousepointer over the sheetname a popup appears with the sheetname "Target".

However: when the code is run it asks to confirm which sheet is needed in the sourcefile. The name it gives is "_Target"

Is this "_" the problem and how can I get rid of it?

I have added a demo to demonstrate what happens

How can I fix this?

Thanks in advance
Hein