Please help with forwarding and email but not actually sending it

Hello,
I’m a newbie and trying to create my first script. I have combed through many existing scripts and tried to modify them to meet my needs but am not having much success.

My goal is to forward an email (in mac mail), or rather to create a forwarded mail but not actually send it as i have to include an attachment with it. I have my own business and am trying to expedite my invoicing process. I always get Purchase Orders from one specific email address. I usually click the “forward email” button (to keep the PO number in the subject line) then attach my invoice file and send to the processing person.

The script I am trying to make will create a new forwarded message whenever i get an email from from address “a”, the message will be addressed to email “b” and keep the same subject. It will include the text “Hello,
Please apply the above PO number to the enclosed invoice. Thank you.” Once i manually locate the invoice file, and attach it I can manually click the send button. Is this possible?

This is what I have so far…

{
tell application “Mail”
set theMessages to the selection
repeat with thisMessage in theMessages
set newMessage to make new outgoing message at end of outgoing messages
tell newMessage
set content to "Hello,
Please apply the above PO number to the enclosed invoice.

Thank you"
set subject to thisMessage’s subject
make new to recipient with properties {address:“AddressB@Domain.com”}
end tell

	set read status of thisMessage to true
end repeat

end tell}

What am I doing wrong? Please help.

Thank you!