PRTG -> SSH -> Script

Hello,

I would like to have PRTG monitor how many leases I have taken up in a pool. Currently I have a script that runs from the Operational CLI:

#!/bin/vbash
/opt/vyatta/bin/vyatta-op-cmd-wrapper show dhcp leases | grep '10.9.8.' | wc -l
exit 0

For PRTG to be able to run a script, I neet the script in /var/prtg/scriptsxml/ and I did try that, but it errors saying it doesn't know what to do with "show"

Any ideas?