Attaching Wall to Underside of Beam

[nsinha73]

How can I attach a wall to the underside of a sloped beam...The Roof occurs on top of Beam but wall framing is under this Steel Beam....Other framing happens here but.....my question is
How can I offset my wall attachment profile to follow underside of Steel beam, without editing the Wall profile?

[dhurtubise]

Draw a ref plane and attach to the ref plane