Possible to link battlelog for PC and 360?

Yes, this is possible and can be done by yourself if the Xbox account hasn't been linked to another Origin account previously.

Follow these steps and it should link both account together:

1. Log in to your Origin account

2. Click Friends -> Add a friend in the menu bar

3. The pop-up will allow you to log in with you Xbox account details.

4. Fill in your log-in details and follow the steps on screen

5. If everything went fine, you should be able to see your Xbox account listed under Connected Accounts in your account management page (click Account and Privacy in the menu bar or on https://www.origin.com/account).

If your Xbox account was previously linked to another Origin account or if you encounter any issues with the steps above, please contact a Game Advisor at https://help.ea.com/contact-us for further assistance.

Just as Dennis said this is possible - I currently have one PC soldier, 2 PS3 soldiers, and 1 Xbox soldiers all of varying ranks under my Origin account.  However you must be aware that the Xbox soldier is completely seperate from your PC soldier and your stats and unlocks will not transfer from your Xbox soldier to your PC soldier.  Your PC soldier will be a brand new soldier beginning at level 0 and you will have to re-earn everything on your new soldier.  Also, if you have purchased any DLC for Xbox such as Premium or expansions, shortcut packs etc they too will not transfer to your PC soldier since they are platform specific.  If you want DLC on PC that you currently have on Xbox you will have to purchase the DLC again on the Origin store.