I need to concatenate data vertically in each row and per column (i.e retaining all data in merged cells, not just from top most cell) based on merged rows with a serial number in column A.

So I have:

A B C D
Data1 Data2 Data3
1 Data4 Data5 Data6
Data7 Data8

2 Data9 Data10 Data11
Data12 Data13

3 Data14 Data15 Data16
Data17


I'd like to have:

A B C D
1 Data(1+4+7) Data(2+5+8) Data(3+6)
2 Data(9+12) Data10 Data(11+13)
3 Data14 Data(15+17) Data16

Could you please help me with a macro for that?