Each node as a source of injection


here , at each iteration, a node is randomly selected as the injection source. What should I do if I want to choose one of the nodes as a source injection instead of randomly selection?
I mean suppose that each node has a sensor and each iteration only one node be a source of injection .
I have 24 different start time for each of them ( An injection is made per hour for each node). So, in a net with 36 nodes, means that I have 36x24 different scenarios and each scenario has 36 different node’s Quality results.
I do not know what to do, please help me. Thanks for reading.
my try is the following but It’s not work.

    for node=1:G.NodeCount
        for startTime=1:24            
            G.setMSXSources(node_id(inj_sc(i,1)), 'AsIII', 'Setpoint', inj_sc(i,2), 'AS3PAT'); % Specify Arsenite injection source
            G.setMSXPattern('AS3PAT',as3_pat); % Set pattern for injection
            Q{node,startTime} = G.getMSXComputedQualityNode(sensor_index); % Solve hydraulics and MSX quality dynamics            
            G.setMSXSources(node_id(inj_sc(i,1)), 'AsIII', 'Setpoint', 0, 'AS3PAT'); % Reset injection source