How to recover deleted text messages iPhone 3GS?

[Max]

I have an iPhone 3GS. I accidentally deleted my texts with my girlfriend. She and I have been talking for a long time now. It's been about a month since I last synced my iPhone to my PC. So, there's a lot of text messages that have gone by between now and the last time I synced my iPhone. Is there any way for me to recover what I lost on my phone? I'm afraid to sync my iPhone to my computer because I don't want my current messages on my iPhone to replace what's already in the backup on my PC. I want the messages that are already in my backup + the messages that I accidentally deleted after the backup was created + the messages that I currently have on my phone. Also, I want to restore all of these messages into my iPhone. I don't want to just be able to view them on my computer. Is this possible? If so, how?