[AccessD] "Find" combo box searches more than one table

UNION the pair of SELECT statements, each point to one table. Grab the
second column to know the location of the hit. Assuming that both tables
have similar structures, open the edit form passing the appropriate args,
i.e.
DoCmd.OpenForm FormName:= {arg1}, WhereClause:= {PK-column} = "your value"

HTH,
Arthur