1.

this is a question for worksheetfunction newsgroup
as it has nothing to do with (VBA) programming..

2.
basically it's VERY simple.
the match and the (H/V)looKup functions will interpolate
unLESS told not to.

5 6 7 8
2 62.6 72.4 81 92
3 51.2 60 70 80
4 40 50 60 70
5 30 40 50 60

2.5
5.5 62.6
=INDEX(B2:E5,MATCH(A7,A2:A5),MATCH(A8,B1:E1))


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wrote :

5 6 7 8
2 62.6 72.4 81 92
3 51.2 60 70 80
4 40 50 60 70
5 30 40 50 60