Catalog client script differences

Catalog client scripts are very similar to standard client scripts, with a few important differences.

Value
 Instead of selecting a table such as Incident for the script, select a catalog item or variable set. As your system may have a large number of catalog items, you should select a catalog item or variable set using a reference field instead of the choice list that the standard Client Script form uses. 
 When using an onChange() catalog client script, it is linked to a particular variable instead of a field. The system automatically populates the variable name selection list with any named variables from the catalog item or variable set selected.