You can determine whether a handle value exists on the database by using a standard function rule or an activity.
You can call the standard function rule pxDoesHandleExist() in the Utilities library to determine whether a specific instance exists in the database. The pxDoesHandleExist function accepts as a single parameter, a text value containing the candidate handle, and returns true or false. The clipboard is unchanged. The function execution is faster than using an activity as described below.
Alternatively, you can create an activity that uses the Obj-Open method and tests whether the instance was found.