I know this is very old -- but a possible solution would be to use programmable logic and virtual dosing pumps to control a virtual switch and that virtual switch to control the actual dosing pump connected to the peroxide.

Code:
Virtual Doser 1 Schedule
            OR        -------->1 OR 2
Virtual Doser 2 Schedule
                                 OR-----> VIRTUAL SWITCH -----> ACTUAL DOSER
Virtual Doser 3 Schedule
            OR      ---------> 3 OR 4
Virtual DOser 4 Schedule