Rate of Change Acceleration/Deceleration

Hi. If one is trying to use the ROC on price and trying to utilise the Acc/Dec of teh indicator to detect how quickly price is moving up or down how does one handle it when the one value is above zero and the other value is below zero? So basically one will have a piece of code reading:

double ROCACCDEC = ROC(1)-ROC(5)/ROC(5)

This is fine when both are above or below the zero line, but when you have ROC(1) = -2.5 and ROC(5) = 1.5 then is becomes tricky. How can one handle this elegantly or at all?

Thanks