Mask to create effect of blood dripping

I am trying to create a mask that allows me to go from one texture to the other in translation… What I mean is not by blending like Lerp is doing
I have a texture of the face of my character with no damage, and another face of my character with blood dripping. I would like the mask to create the effect of the blood slowly dripping on the face.
Any idea on how to achieve this result?
Thanks :wink:

Assuming your UVs are aligned with the top of the head at V=1, you could always animate a value to compare against the current V position, and discard pixels outside that range.