Help with Multiple Triggers

I would like to know how I can cleanly do the following in Team City.

Example

Here is the hierarchy diagram of the 4 projects

Project Core
This is a top level project without any references.

Project Lights

•     Project Core

Build Trigger – Finish Build Trigger Project Core

Project Wheel

•     Project Core

Build Trigger – Finish Build Trigger Project Core

Project Ford

•     Project Lights
  
•     Project Wheel

Build Trigger – Finish Build Trigger Project Lights
Build Trigger – Finish Build Trigger Project Wheel

The problem here is that Project Ford will build TWICE, once when Project Lights is triggered and the second time when Project Wheel is triggered.

I would like to know if it’s possible to only Trigger Project Ford once all the project references are built so it’s only triggered once.