Hi Dev and welcome to the forum!
Unfortunately, the only way I know of to sort things in InfoPath is via code. There is a sample InfoPath form that has this code in it and it is very easy to adapt to your own solution. If you're looking for a C#.NET example, I can provide that.
Anyway, I don't know which solution it is, but I'll ask the team and have one of them respond. They'll know better than I will because they were the ones that made the sample solutions that ship with InfoPath!
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge