Expression to pick a team member not already selected

[Tony_Insua]

First post after 2-3 years of not using AppSheet. Thanks in advance. 

I have a "Projects Table" that has a "Project Lead" Column that references the "Project Leads" table which have a bunch of names. In my Projects Table there is another column called "Lab Lead".  I'd like to reference the "Projects Leads" table but NOT show/pick the name of the person who is already selected as a "Project Lead". 

Can anyone help with this expression? 

Thank You

[Tony_Insua]

@Steve Hi, any chance you can help me with this expression I'm looking for? How can I select a team member that is not already chosen on a previous column? Thanks

[TeeSee1]

PROJECT LEADS[project lead id] - PROJECTS[ref to project lead] in VALID-IF

[lynchk21]

Sounds like you could 1) use a slice on the Project Leads table that filters out Project Leads and then 2) use the slice as the reference or 3) as suggested values

1. NOT(IN([Project Lead],Project Leads[Project Lead]))
2. REF_ROW("SliceName","project lead")
3. SliceName[Project Lead]