Can you elaborate a bit more since I don't understand your question exactly I'm afraid.
Is this what you mean?
The XLS column has text values, and you want to automatically pasted to the link column?
The possible values of the link columns are only the values of the primary field in the other table the link column is linked to. You can copy/paste the values of XLS column manually, and when pasting them in the link column the values will be pasted which completely matches the values from the primary field in the other table.
This is a manual action obviously. Maybe it can be done automatically via a script, but my scripting knowledge is too limited currently for that case to really help.
