Find pflow operator in given PF_Source

Is there a way to find a specific operator in a given PF_Source.
Say I have three particle systems. Rocks, Leaves, Dirt
Each of those systems have a birth event and a position-Object operator.

Is there any where I can get the position-Object operator by just supplying (for example) "Rocks"
So I can then set the objects in that operator using maxscript.