Your request is definitely possible, however since it is a Customization request, could you please post to our Customizations Q&A forum? Click here: https://success.clarizen.com/forums/22175706-Customizations
Our Customization Experts monitor this forum regularly and will respond to your question. It will be helpful for them to see what you have tried in the formula field as well to make sure it's not an issue with the system.
Alternatively, you can attend our Advanced Q&A sessions available currently twice per week. These are great resources for free consulting from our experienced Customer Success Managers and visual/interact answers to your questions. Click the following link to register: http://www.clarizen.com/resources/online-demo.html#second