Align work object in Rapid using vertical plane?

I need a work object in a real robot cell at position p1 on the bottom left-hand corner of a plate, which is approximately vertical.

It is not convenient to have three points orthogonal to the plate for teaching the work object.

If I teach the points p1, p2 & p3 I can move Wobj1 to the position of p1 using  'Wobj1.uframe.trans:=p1.trans;' and I can calculate vectors from p1 for an imaginary work object plane orthogonal to the plate.

Is it possible to calculate Euler rotations or a quaternion from the vectors to correctly align Wobj1 with the plate geometry?

Thanks,

Kevin