help appending code to this working script

[virustrapp]

Hello.

So I have this script here

using terms from application “Mail”
on perform mail action with messages theMessages for rule theRule
tell application “Mail”
repeat with thisMessage in theMessages
set msgSource to source of thisMessage
try
do shell script "echo " & quoted form of msgSource & “| /usr/local/clamXav/bin/clamscan --quiet --stdout -”
on error errMsg number exitCode
if (exitCode = 1) then
tell thisMessage
set (background color) to red
end tell
set junk mail status of thisMessage to false (* <<Infected files may not be moved to mailbox “infected” if true )
(
It would go here maybe a do shell script “”
*)
else
display dialog "Something unexpected has happened to clamAV scan: Exit Code = " & exitCode
display dialog “Error Message:” & errMsg
end if
end try
end repeat
end tell
end perform mail action with messages
end using terms from

Now what I want to do is If that message is infected with a virus, I want it to change to subject.

Now the only way I found to do this is

take the email in question
open it in text editor
find the subject line and modify it to whatever you choose… in my case I choose INFECTED then rest of subject
For me the subject line was Subject: [VirusTotal] Server notification
so i modified the subject like this
Subject: INFECTED [VirusTotal] Server notification
Save the file

When I open the file, the subject is changed

So my question is how would it automate this task with appending code to this above script?

EDITED: not sure if this will help but I’m seeing something like
open thisMessage in textedit
get line that contains Subject: [VirusTotal] Server notification (Subject: whatever it maybe)
Add line INFECTED just before subjects begins. but after Subject:
Save file