Sleep_n0m1 Library

My sketch requires that I have 2 functions that will Wake the processor from Sleep.
I am looking at the Sleep_n0m1 Library.
My question is:
Can I run both the "countDown / sleep.sleepDelay(sleepTime)"
AND
the "Interrupt / sleep.sleepPinInterrupt(intPin,LOW)"
In the same sketch?
I have attempted to combine the two example sketches, but the "Interrupt" does nor work.
Both examples run great when not combined.
Can anyone advise on which is the best solution to have both countdown and external interrupt.