positioning particles sequentially on an object

[jusflem]

Hey folks.  I have a job where I'm trying to send particles from the surface of one object to another.
The second object is actually an arm made of 4 separate objects, made from four separate particle flows, but the problem I need solving is the same for all four.
Now I can send the particles to each target object I need using:
Find target
Position object
Object bind
However, at the moment the particles are set to randomly target any point across the whole object.
My question is:  Is there any way I can grow the arm sequentially say from the fingertips up towards the shoulder?
I'm guessing it's a particle position property test and I find a target positioned first at the fingertips, use another find target, looking at the closet point of the object, then somehow test whether enough particles occupy that part of the object, so the find target moves up the arm...
But can I do it? No, sorry, my brain hurts.  Is there anyone out there who is magnificent enough to have solved this issue?

[d4rk3lf]

Well, that might be a little tricky. 
For a start, I would look at this thread, and last post user drawer14 made. 
http://forum.tyflow.com/thread-813.html

He attached the file, where the coins are building in order. 

So, that, with combination of find target should do the trick, I guess. 
But I never tried it.

[drawer14]

Thank you d4rk3lf

yes you will need a similar method, basically you need to tell Tyflow which one comes before the other and there must be an information on how it they are set or look to target their position.
there are multiple ways to do it once you figure out the idea.
the file I did is one way but for example you can send them to another event by surface test that is animated from top to bottom , now they have event age value that you can use as test value to send them one by one.

you will always get a better help if you attach photos of your scene