Trying to use the target machine domain variable in custom Tool

We use Dameware to remote onto three different domains across our support environment. I've setup Dameware remote control as a custom Tool in Inventory that works well in my machine's native domain. Unfortunately the two other domains fail when trying to connect because it's not passing the proper user credential domain. 

I'd like to be able to have PDQ pass the target computer's domain similarly to how it passes the target computer name. Is that possible at this time?

I'm not looking for passing the %USERDOMAIN% variable, since that won't help us for machines that are not currently logged in. I'm looking for a variable that has the target computer domain that can be used in the Tools editor.