Facing error while working with Aggregate function in MDX (MultiDimensional-Expresson)

Hi everyone hope you're doing well I'm using Aggregate function to aggregate the value of my measure for two specific years as you can see below : select aggregate ({[DimTime].[Year].& ,[DimTime].[Year].& },[Measures].[IndentCount]) on 0 from [Procurement] according to the fact that aggregate function accepts two parameters : Aggregate (Set_expression , Numeric_Expression) What is wrong with my MDX query? I get this error : The Axis0 function expects a tuple set expression for the argument. A string or numeric expression was used. Thanks in advance