if spm_jobman('serial',...) asks for an input, you have to specify it. You can either do it via the GUI that pops up, or as additional arguments to your spm_jobman('serial',...) call. See the help of spm_jobman for details. Also, why do you call spm_jobman('serial',...) with just a print job? It might be easier to set up a batch pipeline for one subject via the GUI (without entering subject specific data). There you can insert as many print jobs as you want. From the GUI, you can then save a batch job and a script outline. You would only need to edit the script - enter your data locations and subject specific stuff there and run it.
Hope this helps,