I don't see a picture attached. If the following doesn't answer your question, please ensure to attach something and I can take a look.
Is QQQ just a workspace variable that feeds into a flow source? If so, you can do:
>> QQQ = 40;
>> simout1 = sim('PumpLocation','StopTime','20', ... );
>> QQQ = 50;
>> simout2 = sim('PumpLocatiom','StopTime','20', ... );
- Sebastian
