Software :: Formula Array In Excel For Mac 2011 (Brackets Missing)

I am experienced in Excel VBA on the PC but not on the Mac. I am building an application on my PC that will run on my sister's Mac (latest OS, Excel V14.0.2). The problem involves the use of FormulaARRAY in my code. I have extracted the problem statement into a small example routine shown below:
Public Sub example()
Dim lastcol As Long
With ActiveSheet
lastcol = 12
.Cells(4, 6).FormulaArray = "=SUM((MOD(COLUMN(RC9:RC" & lastcol & ")
-COLUMN(RC9),3)=0)*(RC9:RC" & lastcol & "))" End With End Sub

Here is one of the correct and working formulas that resulted on the PC (note the brackets for the array formulas are missing but they are there. I got what I am showing by using the 'display formulas' option which apparently does not show the brackets):
=SUM((MOD(COLUMN(RC9:RC12)-COLUMN(RC9),3)=0)*(RC9:RC12))

Here is the incorrect and non working formula that resulted on my sister's Mac: (again the brackets are there)
=SUM((MOD(COLUMN(R[5]C[465]:R[8]C[465])-COLUMN(R[5]C[465]),3)=0)*(R[5]C[465]:R[8]C[465]))

Both systems were set to display R1C1 Reference Style. This is irrelevant on the PC and I would assume the same for the Mac. I bought an old G4 for $60 to use to debug my PC code in the Mac environment. Curiously the code runs fine on it under Excel 2004.