The easiest way to generate repetitive bursts of events is by taking advantage of this feature of the NetStim class:
. . . NetStim can also be be triggered by an input event. i.e serve as the target of a NetCon. If the stimulator is in the on=0 state and receives a positive weight event, then the stimulator changes to the on=1 state and goes through its burst sequence before changing to the on=0 state. . . . A change to the on state immediately causes the first spike.
(see the Programmer's Reference entry on the NetStim class).
So just make this toy network:
ns1 projects a NetCon to ns2 with delay 0 and weight > 0 (1 is nice)
ns2 projects as many NetCons to whatever targets you like, with whatever weights and delays you like
ns1.number specifies the number of bursts
ns1.start specifies the time at which the first burst starts
ns1.interval specifies the interval between burst onsets
ns2.number specifies the number of events per burst
ns2.interval specifies the interval between events in a burst
ns2.start = 1e9 so that ns2 remains silent until ns1 tells it to start a burst
With a little cleverness, you could get very fancy with this . . .