Anchor point / Origin point for Scales & Rotation

Hello.
I was wondering if anyone knows how to alter the anchor point of a layer/projector? Similar to After Effects or Photoshop, so you could rotate/scale from a given point. I am looking to scale a video clip up from the bottomcentre rather than the centre.I believe you can alter the HV mode to scale from corners and I've experimented with using calculations, but wondering if there is a simpler way. Would it require adding to a 3D shape?Any help would be appreciated.many thanks,Darius 
There is no way to define the anchor point.
The way you have suggested may be the best approach. 
OK, thanks Graham. I'll have another play with using Envelope Generators and Calculator.

Hello,
I just found an elegant way:– using the new projector, open the mapping, publish in "output", rotation, offset X and offset YIf you put– horz pos = 50– vert pos = 50– Rectangle 1 : Offset X = 1– Rectangle 1 : Offset Y = 0.5If you move the Rectangle 1 : Rotation, the image turns as usualIf you move the projector Spin, the image turns on is cornerAnd all the other possibilities.I think it's what you search.jacques