question

If you want to do it without Process Flow, here are some steps you could take:

• Set the source to release items at inter-arrival time 0, so they get created "infinitely" fast
• On Reset of the queue, set two labels: WaitingForEntry to 100 and WaitingForExit to 80 (or whatever names you want to give them).
• In the On Entry of the queue, decrease WaitingForEntry by one. If this makes it reach zero, call input.close() to stop the queue from receiving more items.
• In the On Exit of the queue, decrease WaitingForExit by one. If this makes it reach 80, set WaitingForEntry back to 100 and call input.open() on the queue to make it start receiving from the source again.

Having said this, I would prefer Jordan's Process Flow approach. Also, a few remarks about your attached model:

object Q1 = model().find("Queue1");

is not going to work, Object needs to be spelled with a capital O. However, you do not need this: you are inside a trigger on Queue1, so you can access the queue through the variable current (that comes predefined on line 2).

Similarly, if you want to get the source (which I don't think you really need) it's safer to use

Object S1 = current.inObjects[1];

to get the object connected to the first input port of current (the queue) such that your code will not break if you later decide to rename the source.

Finally, note that getbatch does not do what you expect: this command is intended for use with Process Flow:

Gets the batch in a Batch activity by token or Group By value.

(emphasis mine).