Make Open Workbook Active Irrespective Of Name

Folks I'm not sure if this is possible but here's what I want to do.

I have two (2) Excel workbooks open.
By activating a VBA macro in one I want to make the other active, copy some data, and paste it into the first workbook.
The tricky part is that workbook I'm copying the data from does not have a static name.
It could be called anything.
Any ideas?

Hi

Extremely open to errors, but something like

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It does assume that the workbook you want to paste the data into contains the macro.

rylo