I have a list of records where the Project Manager has several numbers
assigned to him but sometimes the number is duplicated. How do I use the
CountIF so that it only counts the number once? Here is an example of my
data:

Sales Order Project Mgr
6100517416 Gomes
6100517416 Gomes
6100517424 Gomes
6100517424 Gomes
6100517425 Gomes
6100517425 Gomes
6100521493 DeVivo
6100531944 Sturm
6100531944 Sturm