Select the Macros tab.
Select the macro you want to change.
Choose Properties from the Edit menu.
The Macro Properties dialog box opens.
In the table of Options, select the option you want to change.
The option's name and value are displayed in the Option Name and Option Value fields.
In the Option Value field, select the old value and type the new value for the option.
The new value is displayed in the options table.
Select Notify DHCP Server of Change.
This selection tells the DHCP server to reread the dhcptab to put the change into effect immediately after you click OK.