Two diff files? About how many cells do you want updated and how often do you want to do this?

You could just link the ss to the invoice via each cell, and make a button that turns cell updating on then back off to update. You would want updating off most of the time so that you don't get errors when the other sheet is closed because sometimes excel acts stupid like that. You could also make a macro but 'record macro' makes the ugliest most bloated macros ever. It's been a couple years but I used to make some pretty elaborate stuff for my old job between excel, access, and vb.