Castor Oil paired with using Latisse?

It would be best to continue with one product at a time. If you have further questions contact the clinic where you purchased the product. Best, 

I am not sure I
would recommend using castor oil around the eye areas – it can cause
unnecessary skin irritation in some. If you are using Latisse, and seeing the
results you are hoping for, many people will cut back on their usage of
Latisse, into a maintenance phase that may be 3-4 times per week, although this
is not part of the package label and not what the company that makes the product
recommends. So I would consult your physician, hopefully a board-certified
dermatologist or plastic surgeon, and find out if there are other options that
you can use to your eye areas which are safe and won’t interfere with the use
of Latisse.

I would not combine RapidLash with Latisse. RapidLash is expensive and unproven to work. If your lashes are dry you can apply simply Vaseline to them. It's much better than castor oil. "This answer has been solicited without seeing this patient and
cannot be held as true medical advice, but only opinion. Seek in-person
treatment with a trained medical professional for appropriate care."