How can you apply flux boundary conditions using bvp4c, or bvp5c?

Hello,

I'm interested in solving two boundary value problems, each are second order differential equations, roughly of the form:

y'' = sinh(y) {from x = 0 to x = L}

y_2'' = exp(-y_2) {from x = -L to x = 0}

I have well defined Direchlet boundary conditions at x = -L, and x = L.

I would like to add the following two boundary conditions:

y'(0) = y_2'(0)

y(0) = y_2

Thoughts on how this can be done?

Thanks, Mark