Hi Marco - it is not possible to write an api.Data.Calculate the way you have it with Entity defined on the destination script. You can only write to the current Entity being processed which would be defined in the Data Management step. The best way to do this would be to execute a CustomCalculateRule or DataManagementSequence and passing in the Target entities via the parameter dictionary. Below is an example of this. The initial rule would be ran on the Source Entity to write the Allocation Out and then the target entities are looped over and a Custom Calculate rule is executed on those entities to write the Allocation In. 
Else If args.CustomCalculateArgs.FunctionName.XFEqualsIgnoreCase("AllocationAcrossEntities") Then
	'Calculate the Allocated Out member for ACME (Source Entity)
	api.Data.Calculate("A#Rent:F#AllocatedOut:I#None:O#Import = A#Rent:I#None:O#Top:F#EndBalLoad",True)
	
        'Get a list of target entities to write allocation data to
	Dim entityList As List(Of Member) = api.Members.GetBaseMembers(api.Pov.EntityDim.DimPk,api.Members.GetMemberId(dimtypeid.Entity,"ACMEGroup"))
		'Loop on all the data unit dimensions to trigger the custom calculate
		For Each entity As Member In entityList
		If Not entity.Name.Equals("ACME") Then
			Dim brParamDict As New Dictionary(Of String, String) From {{"Cube", api.Pov.Cube.name},
			                        {"Entity", entity.Name},
			                        {"Consolidation", "Local"},
			                        {"Scenario", api.Pov.Scenario.Name},
			                        {"Time", timedimhelper.GetYearFromId(api.Pov.Time.MemberId)},
			                        {"View", "YTD"}}
			'Trigger custom calculate
			BRApi.Finance.Calculate.ExecuteCustomCalculateBusinessRule(si, "Chapter8Examples", "RentAllocation2", brParamDict, CustomCalculateTimeType.AllInYear)
		End If        
		Next entity
Else If args.CustomCalculateArgs.FunctionName.XFEqualsIgnoreCase("RentAllocation") Then
	'This function is referenced in the previous function 
	If ((Not api.Entity.HasChildren()) And (api.Cons.IsLocalCurrencyforEntity())) Then
		api.Data.ClearCalculatedData(True,True,True,True,"A#Rent")
		Dim totalSquareFootage As Decimal = api.Functions.GetEntityAggregationDataCell("E#ACMEGroup:O#Top:I#Top:F#EndBalLoad:A#SquareFootage:" & _
																						"U1#None:U2#None:U3#None:U4#None:U5#None:U6#None:U7#None:U8#None").CellAmount
		
		api.Data.Calculate("A#Rent:I#None:O#Import = RemoveZeros(MultiplyUnbalanced(C#Local:E#ACME:A#Rent:O#Top:I#Top, " & _
		"Divide(A#Squarefootage:O#Top:I#Top:U1#None:U2#None, " & totalSquareFootage & "),U1#None:U2#None))",True)
	End If