multiple-(BLOB)column, primary key for pre-v 3.23 db

[Brian Warn]

Hello,

I want to use two text columns  as my primary key.  From the DuBois book, I see that I 
cannot do this since my v. 3.22.32 tables are ISAM, and BLOB and TEXT columns cannot 
be indexed.  Besides upgrading to v. 3.23+, is there any workaround to this?  One 
column will simply store really long URL values (300 characters max, I'm guessing), 
and the other column stores graphic image names, probably 50 characters max in length. 
 Any reason why varchar wouldn't work for this?

Thanks,
Brian