Extend Price Rules

The Price rule Group should allow for multiple functions, custom fields (number) and use of intermediate values.

Example: If I have unit cost field value in product, I would want the price rule to calculate the following formula:

Unit Price = [ unit cost x (1 + CF6) x (1+ CF7) ] / (1 - CF8)

So we would require more number custom fields for this, and ability to sleect custom field of the item in the the price rules too.