How to make a texture that blurs?

[PvtRyan]

Hey, I was wondering if it's possible to create a texture that you can place on a brush that has the same effect as the DoF effect in garrysmod? So I just want a texture that blurs the background so I can focus attention on the foreground (machinima experiment). I don't know how to make the VMT for that, I think it has something to do with the rendertarget _rt_FullFrameFB from what I could find, but can't actually get anything working.