Narvin is correct, wheat will gelantanize below the barley mash temperatures. I have done wits using raw wheat and a step mash. Make sure to do a good crush and a protein rest. If you have some starch, Wits are a little hazy anyhow. This is the easy way to do it.
The hard way to do it is to do a cereal mash. Randy Mosher does say that doing a cereal mash with raw wheat will give better mouthfeel. You would do a cereal mash by adding some malted barley to the wheat, crush, bring it to a 155F step and hold for 15-20 minutes, then go up to boil for 30 minutes or so. Stir to keep from scortching. Add back to the main mash.
Jeff Renner covers it better than I can, here, as the Classic American Double Mash in the CAP article. Pay more attention to it that what I wrote above, as my times may be off.http://www.homebrewersassociation.org/attachments/0000/1298/SOzym00-Pilsner.pdf