Update cell from another cell in same form

[mad-q]

I would like to get Access to add the contents from a specific cell from the row above and put the details into the selected cell. I would like this to happen when the user selects either a button of shortcut key.

This is used when we type a part number in and it suggests a different one ( just in case the current is out of stock,) and rather than the user typing the number in get access to paste it in.

I'm not sure it is possible but would love to.

Thanks in advance.
Iain