Append a substring to the end of a string

Question

I'm trying to dynamically generate my "where" clause for a
SQL query. I'd like to append a substring to the end of an existing
string. I tried "ListAppend", but of course that puts a comma
between the original string and the substring. I could use "Insert"
string function, but it seems rather a hassle to have to LEN the
existing string each time I want to append something to the end of
it. Is there an easy way to append a substring to the end of a
string?
Here's an example of the code (using the "ListAppend" that
doesn't work):
<CFSET whereStmt = "ads.ad_duedate + INTERVAL 1 DAY >=
NOW()">
<cfswitch expression="#vendorSort#">
<cfcase value="Yes"><CFSET whereStmt =
ListAppend(whereStmt, " AND ads.ad_vendor =
#AdSortBy#")></cfcase>
</cfswitch>

Answer 1

On additional suggestion...
You can use WHERE 0=0 as the first comparison in your where
clause. This obviously is always true. The benefit is now you can
have as many if statements adding conditions you want without have
to worry about generating an invalid sql statement such as WHERE
AND userid = 5 ie
<cfset var sql = "">
<cfset sql = "SELECT * FROM Users WHERE 0=0 ">
<cfif GetOnlyActiveUsers()>
<cfset sql = sql & "AND Active = 1 ">
</cfif>
Note that there is a space at the end of every line to ensure
separation of statements.