Block on Wedge Problem

[konichiwa2x]

Hi,
A block of mass 'm' slides on a wedge of mass M. The wedge also moves on a smooth frictionless surface. Find the acceleration of the wedge.

I have written down the equations of motion for the wedge and the block but dont know how to proceed further as there are more variables than equations:

a= ax + ay (block)
A = acceleration of wedge

For block:

Nsin\theta = m(ax)
Ncos\theta - mg = m(ay)

For wedge:
B is the normal reaction by the ground on Wedge
B = mg + Ncos\theta

What do I do after this? I think I have to work out a constraint relation here but I am not sure how to do it. Please help.

[Doc Al]

First find the horizontal accelerations involved. What's the relationship between A and ax? Your constraint is that the block maintains contact with the wedge. (Hint: View things from the frame of the wedge.)