I suppose you started with the 'pick nearest' condition. And then you encounterd 2 problems.
1/ 'nearest' picks nearest to a position. The 'nearest' to the position of a sprite is the sprite itself.
2/ What ever else you try to pick under a 'is dragged' condition, only the dragged one is picked. This is just natural, because the 'on dragged' picked that dragged sprite, and for all subconditions that follow, that pick is the Previous Picked Selected Object List. All following subconditions start picking from that Previous Picked Selected Object List. And that is the dragged one.
To solve this, the easyst way is to use functions. Functions start picking from scratch. Always.
Therefor, here is a capX that is based on 'pick the nearest'. Just the show you why it probaly not worked, and the solutions that can be used.
https://drive.google.com/open?id=0B1SSu ... 2txVXc3V0E
But, as TwinBlazar mentioned, it can be easely done by building a distance map first. Here is an exemple of that.
https://drive.google.com/open?id=0B1SSu ... 3hTUVJhT00
Yet you have to solve the same little problems. Lowest distance to a sprites position is the sprite itself. Pick others then those picked by the dragging condition is far way easyst done with functions.