Last activity from child on parent

[steveDel88]

I'm trying to create a formula on a parent object that reflects the last activity date from a child note object.

Parent object = [Client]

Child object = [Note]

There is a 1 to many relationship. 

I have a field on the parent object for "Last Activity" and I would like this to reflect the field "Completed D/T" on the child object for the most recent record. I was trying to use this formula but can't seem to get the syntax to work properly. Thank you in advance.

LOOKUP( MAXROW( SELECT( "Notes[_ROWNUMBER]", (Note[Client] = [Row ID]) ) ), “Note”, “_ROWNUMBER”, "Completed D/T" )

[Kabuliño · Accepted solution]

maybe something like...

INDEX([Related Notes][Completed D/T],COUNT([Related Notes]))

 ?

[steveDel88]

That is exactly what I needed. Thank you!