Are you wanting to use the Shuffle drag modes in Logic?
Here is an explanation from the Apple documentation on how the Shuffle drag modes work as this probably explains it best:
http://documentation.apple.com/en/logicpro/usermanual/index.html#chapter=13%26section=3%26tasks=true
Shuffle L and Shuffle R:
Choose to automatically align regions (to the left or right, respectively) when you move, resize, or delete them.
When you use Shuffle R (or Shuffle L), moving a region to the right (or left) aligns the region end point with the start point of the following region, ensuring that there is no space between the two regions.
Regions that are dragged over each other swap positions.
When deleting regions, the remaining regions (those to the left or right of the deleted region) are moved to the left or to the right by the length of the deleted region.
If a region is stretched or shortened when either Shuffle option is active, the other regions on the track are moved to accommodate the new length.
In Shuffle L mode, the right side of the region is stretched or shortened, and the regions to the right of the edited region are moved.
In Shuffle R mode, the left side of the region is stretched or shortened, and the regions to the left of the edited region are moved. The regions that precede the edited region can only be moved as far as the project start point. If the stretching of a region results in preceding regions being forced to the project start point, and exceeding the space available, the edited region overlaps the existing content.
