I have a formula that I cannot get right and have been working on it
for several days now and would appreciate a "parenthesis" in the right
place.
The background :
I have to calculate the total of a column based on the year of purchase
of an item (depreciated over 5 years) BUT, the first 2 items only get
included in the total if the column year is the year of purchase, i.e.
the first year.

Cells:
o12:w12 contain the years to be totalled for
K15/16 are the years for the first 2 items
K19:K41 are the years for the remaining items
BB15:BB41 are the values to be totalled

all Year cells are custom yyyy format
all cells to be totalled are numeric

I created a grid of valid combinations as follows

K15 K16 Cells totalled
Blank Blank BB19:BB41 *

Blank =o12 BB16:BB41 **
Blank <o12 BB19:BB41 *

=o12 =o12 BB15:BB41 ***
<o12 <o12 BB19:BB41 *

=o12 <o12 BB19:BB41 + BB15 ****
<o12 =o12 BB16:BB41 **

=o12 Blank BB19:BB41 + BB15 ****
<o12 Blank BB19:BB41 *

So there appear to be only 4 sets of calculations I need to make.

I created the following formula but keep getting missing parenthesis
errors.

=IF(OR(AND(K15="",K16=""),AND(K15="",YEAR(K16)<YE AR(O12)),AND(YEAR(K15)<YEAR(O12),YEAR(K16)<YEAR( o12)),AND(K16="",YEAR(K15)<YEAR(o12))),SUM(BB19:B B41),IF(or(AND(K15="",year(K16)=year(o12)),AND(yea r(K15)<year(o12),year(k16)=year(012)),SUM(BB16:BB 41)),if(and(year(k15)=year(o12),year(k16)=year(o12 )),sum(bb15:bb41)),if(OR(AND(year(k15)=year(o12),y ear(k16)<year(o12)),and(k16="",year(k15)=year(o12 )),sum(bb19:bb41+bb15))

Any help or suggestions anyone can give would be much appreciated.

TIA
Fred