Multiple textures in material how do I add an alpha to just one texture sample?

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1

Hi

I’ve made a texture out of 3 texture samples - stone, moss and rock. The moss texture has an alpha - used so you can see the other textures around the edges. How do I link up this alpha to just the moss texture without it effecting the whole material? Is this possible at all?

Thanks!

(I included a link of my progress so far)

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