question

So after examining your question I think I've come with something that might work as an example for what you're doing. The way you can accomplish this is with Dispatcher objects, Labels, and some custom code. (As a side note, I would definitely encourage you to update your FlexSim to the newer versions, as you will find getting some the things done that you need in Process Flow will be much simpler.)

So first of all I set up the the model with the number of Dispatchers equal to the number of groups of Task Executers. Then I set two labels in the first Queue object: one to keep track of which Dispatcher is being called, and one to iterate through the number of operators/task executers in each group. Then I put some custom code within the "Use Transport" field in the same Queue. That looks something like this:

/**Custom Code*/
treenode item = parnode(1);
treenode current = ownerobject(c);
int port = parval(2);
int numOp = getlabel(current,"numOperators");
int disNum = getlabel(current,"dispatchNum");
if (numOp == 0) {
   numOp = 2;
   disNum++;
   if (disNum>3) {
      disNum = 1;
   }
}
numOp--;
setlabel(current,"dispatchNum",disNum);
setlabel(current,"numOperators",numOp);
return centerobject(current, getlabel(current,"dispatchNum"));

Finally I checked the Perform Batching checkbox on the Queue with the batch number equal to the number of operators coming to retrieve the items, so as to ensure that they come in groups to grab the items. (I also set the processors to be able to hold up to 3 items (equal to the number of groups) so that the groups wouldn't just all stand waiting for the processor to finish. You can look at my model here, and copy anything you need from it. Again I would strongly encourage you to get the newer versions of FlexSim. You'll find Process Flow and Lists will be able to accomplish a lot more, with a lot less custom code and managing object triggers. dispatchexample.fsm