Edit a MAC address in the DHCP static table on D-Link 2780

Hi all,
Anyone know how to edit the mac address assigned to an IP in the static address table on this router. I have changed a piece of hardware out and so need to change the mac address to reflect this.
I can't seem to find a way to edit or even delete and entry once it's entered??
It's a talktalk issued router.

Hi.
In the 'Mac Address' table entry select the mac address of the item you wish to change the static address or delete. Then change the status from 'Static' to 'Auto'. click on 'add/apply' and you will get the option to delete the entry. Once deleted you can refresh the table, select the mac and assign a new IP address if required.

Many thanks