using systables in table constraint

In my database, I have a table (foo) which has a column (footable) that stores table names. The tables listed in column footable are used as lookup tables by my application. Is there a way to place a constraint on on footable such that the table name must be a valid table? I tried a constraint that references tabname in systables, but I get error 297. I looked in the sys admin manual and determined that there was no unique index on tabname therefore I cannot place a reference on the column. I tried placing the constraint on tabname and owner, but I get the same error. create table foo ( footable char(18) references systables(tabname) ); Is there a way to guarantee that the table names identified in footable are in the database? ---------------------------------------------------- Seth J Hllman | email: sjhillman@tasc.com TASC | phone: 617/942-2000 x2250 55 Walkers Brook Drive | fax: 617/942-7100 Reading, MA 01867 | ----------------------------------------------------