parent assembly in BOM

I'm currently at a place that want the parent assemlby number (file name) listed on each child drawing. Currently, this is done by manually filling a custom property box in the child model & linking a text box it in the child drawing to the child model custom property.

Is there a slick way of automatically filling in the parent assembly number in the child drawing to eliminate (well, reduce) user input errors?

Thx

SolidworksBill Of Materials