Catching 'print' event for Item Fulfillment

I had a task recently to capture the 'print' event when printing a packing slip, either using the 'Print Checks and Forms' feature or using the 'print' link directly on an Item Fulfillment Record.  I got it working and thought I'd share my findings in case this helps anyone else.

When printing an Item Fulfillment Record (IFR), you would think that the 'print' event would fire in the script attached to your IFR custom form.  But that is not the case.  What happens is that the 'print' event fires in the Sales Order script with the sales order associated with this IFR.  In order to find the IFR that has been printed, you use the 'shipid' body field.  This field contains the Ref No. (tranid) of the IFR.  You can then perform a search for that tranid and load the actual IFR record from there.