Dude! you're a legend this is exactly what i was looking for!

By giving it a look i can see how it works (more or less) and I think that I can now solve another problem I have encountered trying to display numbers.

If I have 0 stock of a product there will be no expiry date in ANY box of that product... and of course that would return the numerical value of 0 - the numerical value of the current date, correct?
[so for right now 27/10/15 and time 23:34, the "days left" box returns the value of "-42304" ]

So Ill probably need to include a bit more of an "IF" statement indicating that if there is no value in the boxes targeted, it should return nothing. (am I on the right thinking here?)