Enable trigger mode and use 'Latch" setting. Exactly what you want. Hit a button. The sample wil play over and over and over until you press the button again.
I owned ESI-32 and looking at specs the trigger mode is identical. Basically turns the num pad on the front panel of ESI into trigger buttons. Check the manual for more details. In fact, always check the manual. It's all in there.

-ED-
[This message has been edited by 3351 (edited 02-06-2007).]