run macro when a cell is changed by the timeof day

I have a macro that runs a clock with the time changing every minute. When the time reaches certain times throughout the day, cells change from a zero to a 1. i.e. at 08:00 cell S7 changes to a 1. At 09:00 Cell S14 changes to a 1 and so on.

When any cell in the range S7 through S28 changes to a 1, I want Excel to call my macro 'Call Send_EMail'

Thanks