Hi Gareth!
Thank you for reaching out! The syntax for an If statement in Clarizen is If(Condition,TrueResult,FalseResult/Else). You can find more details here - http://usermanual.clarizen.com/clarizen-functions$If_Function_Samples.
Regarding the Group, I'm not sure I fully comprehend the use case, I would suggest joining to one of our Advanced Q&A webinars that are being held twice a week. You can register here: http://www.clarizen.com/live-demo.html - I'm hosting the one tomorrow so feel free to join!
Warm Regards!
Tamir