No, there are no select triggers. The closest thing is an rpc-based proxy table.
You could use an insert, update, or delete trigger though. Client would have to be programmed to first perform an insert, update, or delete before doing their select, this could be a dummy operation like "delete mytable where 1=0". But it would be just as easy (and more standard programming style) to just havethe client call the procedure before doing the select in the first place
As a side note, ASE triggers are "after" triggers - their action takes place after the client's statement has affected the table, and the trigger's view of the table data reflects those changes. The SQL Anywhere product supports both before and after triggers.
-bret