Static binding and srx100

Hi

I have an srx100 firewall set up by a another. It is used for PDQs so used static binding for the Mac addresses of the PDQs to set addresses etc etc.

I'm wanting to change some of the old mac addresses for the old machines to new ones but to no avail.

Using the clear command for the system services dhcp binding and enter the desired address returns unable to clear a static binding.

What am I doing wrong?

Thanks