Pivot table; calculated fields HELP please

[endlessboundless]

So have a pivot table; with one column called 'sum of hours' and the other called 'total sum of actual hours'. The 'sum of hours' for each employee is separated as either OPEX and CAPEX. What i'm looking to do is get a CAPEX rate, so CAPEX 'sum or hours' / 'total sum of hours'.

I've looked online at various tutorials but can't seem to find an answer! I know the answer to this may be quite simple, but i can't figure it out!!!

Any help would be greatly appreciated.

TIA
A