A custom report not getting triggred from documeset at the time of ship confirm

Hi There,

We have developed a custom report which has three parameters..organization code, trip id high and trip id low.

This report is assigned to a shipping document set and when we are manually printing the document set by clicking on print doc set button on shipping transaction form, the report is getting launched but at the time of ship confirm, getting the following error.

Error: Trip Name High is a required argument for XXX Report. Please specify a value to Document Set Submission or define a default value for this Concurrent Program parameter.

This is strange as with the same parameter it is working when we print by clicking on Print doc set  the button.