Packing particles without (too much) intersection

[NNois]

Hello,
I'm scratching my head for a long moment without a solution.
I'm not realy good when it's coming to arrays, context mismatch, maths...

Basicaly I have a 3D grid target cloud and a surrounding particle emitter (cubes).
I want my outer particles flying and fill/pack in the 3d grid without intersecting.
all that is simulated by bullet

What I did at start
- Getting from the point targets the first closest emitted particle, store the ID
- Getting from emitted particles the closest point on the 3dgrid on select to one who match this particle ID
-> but i end up whith many particles who can't enter in the volume

I've tested other maners but ended with too complex setup or with context errors...

Did someone already do that ? What do you think, is it doable ?
thanks