Если данные в A1: A10, вы можете использовать =SumProduct(A1:A10,A1:A10,A1:A10)
Если вы хотите написать udf
Function SumCu(r As Range) As Variant
Dim dat As Variant
Dim sum As Variant
Dim i As Long, j As Long
dat = r.Value2
sum = 0
For i = 1 To UBound(dat, 1)
For j = 1 To UBound(dat, 2)
sum = sum + dat(i, j) ^ 3
Next j, i
SumCu = sum
End Function
или более обычно
Function SumPwr(r As Range, Pwr As Single) As Variant
Dim dat As Variant
Dim sum As Variant
Dim i As Long, j As Long
dat = r.Value2
sum = 0
For i = 1 To UBound(dat, 1)
For j = 1 To UBound(dat, 2)
sum = sum + Val(dat(i, j)) ^ Pwr
Next j, i
SumPwr = sum
End Function