Quake-like viewmodel bobbing

My friend wants to do an quake-like viewmodel bobbing, but he has no idea how.
The effect he is trying to achieve is this:

Any help would be appreciated

Change the way the following functions:
function SWEP:GetViewModelPosition( pos, ang )

return pos, ang;

Alternatively you may be able to modify the positioning with PreDrawViewModel

Oh, thanks Acecool, but he did that 5 secs ago using the same functions.

Still, help appreciated.