MS Access update query: how to concatenate 3 fields with criteria

I am trying to design an update query in MS Access that will concatenate up to 3 fields, 2 with criteria. This is for a catalog where the same product might appear on 1, 2, or 3 pages. The query would put the result in another field called CAT_Pages. Since I don’t know Access that well, I’ve accomplished this by running 3 separate update queries and know that there must be a better, more elegant way. Can someone enlighten me?

Query 1
CAT_Pages = [CAT_Pg1]

Query 2
CAT_Pages = [CAT_Pg1] & “,” [CAT_Pg2]
Criteria is [CAT_Pg2] > “1”

Query 3
CAT_Pages = [CAT_Pg1] & “,” [CAT_Pg2] & “,” [CAT_Pg3]
Criteria is [CAT_Pg3] > “1”)

The field CAT_Pages is only used for reporting and printing and needs no further manipulation.