Your use of the word "drawing" in that first sentence may be a bit misleading. When you say you always "export the BOM list from the assembly drawing", are you talking about the actual assembly model file's BOM or are you talking about a Parts List in the drawing file that is representing the assembly in its views? Then I assume it is exported as an Excel file, right? Also you use of the term "form" is confusing to me. Do you mean that you leave the title and column headings of that exported data, but get rid of all the data in the other cells, so that it must all be somehow filled in after you insert it into the drawing as a Parts List? Or have you developed a VBA UserForm in Excel's VBA Editor that you want to use to fill in Parts List data? If we were to create code to fill data into cells in an Excel file, we would need to know the full path & name of the Excel file, the sheet/tab name, how everything is laid out on that sheet, so we know where to put the data, and what all data we will be putting into each of those cells. It is potentially fairly complicated to do it that way, depending on your needs. I don't think you can specify a 'Template' to export an assembly model BOM by, but I do believe you can specify a 'Template' file so use when exporting a drawing's PartsList out. Maybe that could somehow work for your process.
Wesley Crihfield

(Not an Autodesk Employee)