GuardLogix Function Blocks

I understand that GuardLogix is a SIL 3 PLC, I am relatively new to PLCs however have been require to look into GuardLogix Functioality. In particualar i am looking for a function block that can do 2 out of 3 voting i.e. i have 3 level transmitters and the block would pick the best 2

Any help whatso ever is greatly appreciated