Intel Rapid Storage Technology on two separate HDDs

So I have everything set up to use ISR. It is in fact working on one of my HDDs right now. The dilemma is that I have a second HDD I want to do the same thing with but it looks like I can't set it up on two different HDDs.

Here is how I am set up:

Two 2TB HDDs

One 120GB SSD split into two separate 60GB partitions

One of the SSD partitions is set up to cache one of the HDDs. I want to use the other partition to cache the other HDD but see no option to set it up on another drive.

Anything I am missing in order to do this / any workarounds to allow this to work?

Thank you