How to insert field from form into subject line of email

I have a form:

http://www.mcw.edu/FileLibrary/Groups/HMGC/Forms/HIPAAForms/HumanSequencingTertiaryAnalysi .pdf

and I would like to have the name of the person fill in automatically in the subject line.  Right now when the email button is clicked the subject line reads: "Submitted Human Sequencing Tertiary Analysis Submission Form."  Once the form is filled out, I would like the subject line to read: "[PI-Name] - Submitted Human Sequencing Tertiary Analysis Submission Form,"  (as highlighted below)

event.target.submitForm({cURL:"mailto:?subject=[PI-Name] - Submitted Human Sequencing Tertiary Analysis Submission Form&body=Please find attached the completed Human Sequencing Tertiary Analysis Submission Form.",cSubmitAs:"PDF",cCharset:"utf-8"});

I read the other discussion on this, but it didn't seem to pertain to me, or I just couldn't figure it out.  Anyone have any ideas?

Thanks, Anne