The script must return the boolean value true to skip the backup.

Anything else including an error will be considered as false. 

User interaction like display dialog is not allowed.

The custom condition has the lowest priority after time range (highest)

and network connection.

For example check for a specific IPv4 address;

set ipV4Address to IPv4 address of (system info)

if ipV4Address is "00:11:22:33:44:55" then

return true -- skip backup

else

return false -- run backup

end if

Note:

Be aware that the script is called from the local domain, not from the

currently active user. Calling the script in the home folder of a specific

user while the user is not logged in could cause unexpected behavior.