I don't quite follow what you're saying there. Do you want more single missions with convoy attacks? If so, browse through the Downloads section here, specifically:
http://www.subsim.com/radioroom/down...hp?do=cat&id=5
If you're wanting to make your own missions, you'll need to use the Mission Editor. You can try this guy's PDF download:
http://www.wolfwillow.com/nu/westwin...sguide_v06.pdf
Of which there is a v17 out there somewhere that I can't find right now... Or you can browse through this fellow's guide:
http://rangerx3x.blogspot.com/2011/0...n-editing.html
Or even this one:
http://forums.ubi.com/showthread.php...ission-Edditor
If I can find a download for that v17 Manual, I'll link back, or else you'll see a PM from me with a link...