There are several ways you could do it but the way I'd do it would be to modify the report header template.
1) In the pc-dmis install directory is a folder called 'reporting' - back this up.
2) In the reporting folder find File_Headr.lbl - Right click on this, select properties and uncheck Read Only
3) In pc-dmis, File>Reporting>Edit>Label Template - open File_Header.lbl
4) The Label editor opens, you should see what looks like the report header
5) Click on it once (selects it)
6) Double Click on it (allows edits)
7) Click in the cell you want (=SERIAL_NUMBER)
This expression (=SERIAL_NUMBER) is tied into the Ser Num field in the edit window.
8) Right Click to bring the properties for that cell up
9) Change the Cell Expression (=SERIAL_NUMBER) to =VARIABLE("V1") where V1 is the name of your pc-dmis variable, note: you need the ""'s around the variable name, note also all expressions are case sensitive and are all UPPER CASE
10) Okay it, then save and close
Jon Done
Edit to add: bear in mind this will change this report template for all part programs, so if you have programs which son't have the serial number variable in then this field will be blank
Edit again: You need to refresh your report. If you want an automatic print out, switch of the usual printing and insert a print command.
