Getting the correct avg. in a pivot table

[zonemaster88]

Hi, I am trying to get the average cost of items with duplicates of the same item but having different value in a pivot table. I tried looking for an answer on here and was unable to find one.

Ex:
[TABLE="width: 142"]
<colgroup><col span="2"></colgroup><tbody>[TABLE="width: 256"]
<colgroup><col><col span="2"></colgroup><tbody>[TR]
[TD]Date[/TD]
[TD]Item #[/TD]
[TD]Value[/TD]
[/TR]
[TR]
[TD="align: right"]1-Sep[/TD]
[TD="align: right"]1594[/TD]
[TD="align: right"]$100[/TD]
[/TR]
[TR]
[TD="align: right"]1-Sep[/TD]
[TD="align: right"]5135[/TD]
[TD="align: right"]$75[/TD]
[/TR]
[TR]
[TD="align: right"]1-Sep[/TD]
[TD="align: right"]5461[/TD]
[TD="align: right"]$985
[/TD]
[/TR]
[TR]
[TD="align: right"]2-Aug[/TD]
[TD="align: right"]7484[/TD]
[TD="align: right"]$356[/TD]
[/TR]
[TR]
[TD="align: right"]6-Apr[/TD]
[TD="align: right"]8789[/TD]
[TD="align: right"]$125[/TD]
[/TR]
[TR]
[TD="align: right"]15-Jul[/TD]
[TD="align: right"]5135[/TD]
[TD="align: right"]$502[/TD]
[/TR]
[TR]
[TD="align: right"]28-Feb[/TD]
[TD="align: right"]1289[/TD]
[TD="align: right"]$714[/TD]
[/TR]
</tbody>[/TABLE]
</tbody>[/TABLE]

A pivot table would get the average of $408 when I sort by date. However, the average I am looking for is of all the orders with 5135 combined. This would be $476. I understand that I could just sort this by item # but the actual data I'm working with has over 80,000 items (in-practical). Anyone know how to combine item numbers and get the average of combined like items in a pivot table?

Thanks!

 

[zonemaster88]

Sorry, data would look like this

Date Item Cost
8/5 4512 $225
8/5 4514 $425
8/5 4518 $125
8/5 4518 $225
8/5 4504 $375

Average on Pivot $275
I want 4518 combined to get table avg of $343.75