Quote from Excel Help:
Guidelines for using 3-D references
You can use 3-D references to refer to cells on other sheets, to define names, and to create formulas by using the following functions: SUM, AVERAGE, AVERAGEA, COUNT, COUNTA, MAX, MAXA, MIN, MINA, PRODUCT, STDEV, STDEVA, STDEVP, STDEVPA, VAR, VARA, VARP, and VARPA.
3-D references cannot be used in array formulas.
3-D references cannot be used with the intersection operator (a single space) or in formulas that use implicit intersection.