VBA Data Validation

Hi,

I'm trying to build some data validation into attached table. The sheet will be locked down except for the two orange columns where the user will have to record either a % in column D or a whole value in column E. I already have data validation on these cells to allow only of these cells to be completed per row.

I need some form of additional validation that will only allow the value in column to be more than 10% of column C if column B has a value. If column B is blank, the calculation in column F must be less than 10%. To make things a little more complicated, Column B has a VLOOKUP formula in it, so won't be truly blank.

Is this possible?