how can I merge a blending effect layer to another layer in animate?

I've created 2 layers in animate - one with colour, the other with 'multiply' blending effect applied.  I want to create a mask so both layers can be revealed but to do this I have to merge the layers into one, however when I do this, I lose the blending effect.  Does anyone know how I can merge the layers and preserve the multiply blending effect of the layer?  Thank you in advance!