Hello, Would someone be kind enough to tell ...

[Joseph_Corbett]

Hello,

Would someone be kind enough to tell me what I have wrong in this expression? =IF([_THIS]=LOOKUP([_THISROW].[IDKEY],Hours Worked,IDKEY,Concat),

TRUE,

NOT(IN([_THIS],Hours Worked[Concat])))

The [IDKEY] is the actual key in the table I am trying to make sure has no duplicate entries in.

The [Concat] column is a column I am trying to make sure has no duplicates once the row is added to the table.