Require formula for lot wise sum.

[nitishshr]

I require specific formula for lot wise sum of ID .
The ID will re-occur but the re-occurred ID should be separately addition-ed.
The ID will be nearly in 2000 number.
# Do not sum all the similar Structure ID
#Do not change the Structure ID
[TABLE="class: grid, width: 500, align: center"]
<tbody>[TR]
[TD]Structure ID[/TD]
[TD]Weight[/TD]
[TD]SUM[/TD]
[/TR]
[TR]
[TD]A[/TD]
[TD]1[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]A[/TD]
[TD]1[/TD]
[TD]3[/TD]
[/TR]
[TR]
[TD]B[/TD]
[TD]2[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]B[/TD]
[TD]3[/TD]
[TD]5[/TD]
[/TR]
[TR]
[TD]G[/TD]
[TD]3[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]G[/TD]
[TD]4[/TD]
[TD]7[/TD]
[/TR]
[TR]
[TD]A[/TD]
[TD]5[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]A[/TD]
[TD]6[/TD]
[TD]11[/TD]
[/TR]
[TR]
[TD]B[/TD]
[TD]7[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]B[/TD]
[TD]6[/TD]
[TD]13[/TD]
[/TR]
[TR]
[TD]R[/TD]
[TD]4[/TD]
[TD][/TD]
[/TR]
[TR]
[TD]R[/TD]
[TD]3[/TD]
[TD]7[/TD]
[/TR]
[TR]
[TD]G[/TD]
[TD]2[/TD]
[TD]2[/TD]
[/TR]
</tbody>[/TABLE]

 

[Special-K99]

How do you get 3 in the second row of SUM ? I make 1+1 equal to 2

 

[Special-K99]

in C2
=IF(A2=A3,"",SUM(B$1:B2)-SUM(D$1:D1))
and copy down

 

[nitishshr]

Thank you Special-K99.

 

[nitishshr]

I was unable to edit . after posting it.

>>(2)

Thank you once again.