SSRS group total with semi dirty data - reporting-services

Question

Data is Bill of Lading where I have to report items as well as lots and counts. Actual data is sent by other system that mixes total weight of an item on each line of lot details. I receive a textual generation of each Lot # and count from that lot per line on each line. Did I say dirty data?
I have grouped in a sub tablix to show only one item at a time just fine.
Now I need to get a total weight for the truck load. How do I Sum ONLY the first value for that item and skip all the second, third,... lots that comprise this item for my Tablix summary? Data below should show 8343 in the total weight.
Usually have 2 lots per item, may only be 1 lot 10% and may be more than 2 lots 15% of the time.
Will usually have at most 4 items per truck with most 75% of all trucks holding only 1 or 2 items.
item weight LotQuantity
ABC123 4655 4502052014 - 1200, 4512052014 - 2400
ABC123 4655 4502052014 - 1200, 4512052014 - 2400
ABC122 3688 4502052014 - 600, 4512052014 - 1200
ABC122 3688 4502052014 - 800, 4512052014 - 1400
TIA

Answer 1

Created functions in report code:
Dim wgt1 AS Double
Function addWgt(ByVal value AS Double)
wgt1 += value
End Function
Function getWT()
return wgt1
End Function
Dim Cnt AS Double
Function addCnt(ByVal value AS Double )
Cnt += value
End Function
Function getCNT()
return CNT
End Function
In an empty column I added the current weight as well as the current count via the addWGT()
For the report footer I just put in =Code.getWT()