I need a sum function that takes data from a matrix and sums certain row tother

Example)
Data is in cells A1,B1,C1,D1,E1,F1
and A2,B2,C2,D2,E2,F2

I need the vba to in cell A3 sum A1 to C1
then in cell B3 sum B1 to D1
then in cell C3 sum C1 to E1

then do the same thing for the next row beginning in Cell A4

Please help!