1.You can assign the sample on two pads and have one set to Note Off and the other set to One Shot:
For Note Off: Mode> PAd 7(highlight the sample name assigned to the triggered pad)>Window> change from One Shot to Note Off.
2. Another option would be to place the entire program to Mono instead of Poly. Createtwo copies of the samples make your edits to one by trimming the sample to your desired stop point. Mode>F3> Play: Poly change to Mono: this will cut off the sound of the pad once the next pad is triggered.
3.You can create two copies of the sample and trim them according to how you want them to trigger.