ok so you're going to visually go through your list of possible append records and search your existing data (by hand) to see if you have something matching.
the type of search you're talking about isn't going to be automatic, how would your process know to pick up the SMI rather than, say JOH.
If you're talking about building a manual process, where you import your excel information to your table as a temporary record (you can have a yes/no field that indicates whether it's permanent or not) then cycle through the 'new' records one by one then manually type in a search string for your 'permanent' record THEN make your decision about keeping or discarding it, yes, that can be done.
Code:
tblTest
PK LastName FirstName Perm Address
1 Mouse Mickey Y 101 Mouse Lane
2 Jagger Mick 202 England St
3 Mouse Mickey 101 Mouse LN
4 Mouse Minnie 101 Mouse LN
I think I'd build an form where you could pick a 'new' record (one with an empty or N in the PERM flag field) from a list box (because I don't like continuous forms)
then have another list box that had a search ability to search only existing records (ones with a PERM flag of Y) for any string you're looking for so your criteria for that would be
like * & forms!formname!searchfieldname & "*"
and you'd use that as a criteria for last name OR first name OR address