Previously selected as of when? Last time they came to the page? Last week? Last year? Are you going to store their previous selection in a database? How are you hoping to hang on to this? Give more of the scenario of what you're doing.
Since you are using the selections to perform the search, use those values to determine whether or not each option should be selected or not. Example:<BR><select name="sel1" id="sel1"><BR><option value="myoption" <%If Request("sel1") = "myoption" Then%>Selected<%End If%>><BR></select><BR>That's a simplified version of what you'll be doing, but you get the idea.