Creating a "section" of alpha on texture by demand
 

So, obviously i have a bit of a problem with the Castbar time collapsing with the pet frame, but don't like using a different place for aestethics.
So i've thought about, if it would be possible to kind of set an alpha background behind the time and "burn" through the pet frame.
At first i though a Mask texture is what i'd need, but i guess that's not the path to go.

Is that even possible?

It's unclear to me what you're trying to do from the screenshot and your description, but you can give the illusion of making a section of a texture transparent by placing two textures side by side, changing the alpha of one of them, and using texture:SetTexCoord to keep the images aligned if needed.

I want to make the health statusbar of the pet (the green bar on the top left) see through, but only on the area behind the castbar time.

The "issue" i have here, that this is basically "my/default setting", the width/height & placement of the UFs can be set by users, so with that in mind i have to keep in mind that basically the layout could be very different.
Thanks for the info.