macro to copy cell with adjacent cells from other workbook

[acounter2]

I'm sorry to confess that I need some more Excel macro help.

How do you create a macro, which checks if 123.xls file is open and if not opens xls and and waits there user cell selection with mouse and confirmed with enter key and then copies selected cell with 2 adjacent cells from right to the 1st workbook cell (accordingly abc) where the event was initiated.

 

[acounter2]

Hello

The macro seems to be rather complicated
But any ideas how to start? Some macro components perhaps, which are expected to work toward my task? Then I could try to bind these together ...

Thanks in advance!