You can specify an SQL UDF in the select list of an SQL request. As if true of other expressions in a select list, you can also alias an SQL UDF. In this request, the aliased value expression cve is specified as cve in the select list and in the WHERE clause.
SELECT test.value_expression(t1.a1, t2.as) AS cve, cve+1 FROM t1, t2 WHERE t1.b1 = t2.b2 AND cve = 5;