Create Subtotals Dynamically

I am trying to dynamically create subtotals base on values in a column. I also have to group by year. I have gotten the group by year. I used the (previous function) to check for the year and col1 not being equal. I am getting the first subtotal back, don't know how to proceed in my function to return the remaining subtotals



i.e.

col1 col2 col3

aaa 111 2005

bbb 222 2006

aaa 333 2006

ccc 444 2005

ccc 555 2006

bbb 666 2006

bbb 777 2006

ddd 888 2007



2005

aaa subtotal: 1

ccc subtotal: 1

total: 2

2006

aaa subtotal: 1

bbb subtotal: 3

ccc subtotal: 1

total: 5

2007

ddd subtotal: 1

total: 1

grandtotal:

aaa 2

bbb 3

ccc 2

ddd 1

totalnumber 8