Barry,
In P6 you cannot weight your WBS/Activities without cost otherwise your summary band will always have zero %. I recommend using man-hour as cost by setting Price/Unit on resources say $1.00/unit. Alternatively, remove effective date, max unit/time and Price/unit by deleting the data under resource-> Unit & Price tab. The under Project Window-> Calculation tab = enter 1.00 as a default Price/Unit for activities without resource or role Price/Units. This automatically compute your hr or unit = budgeted cost.

Hi Barry,
Waseem is correct that Top Down Estimation is another way to weight and spread the cost to WBS and Activities using resource. You need to apply this for each WBS to have accurate distribution and should have only one resource define for each WBS otherwise you need to compute how many units for each resource to arrive on the expected weightings. Also be aware that using top down estimation will possible over allocate your resource max unit/time that prevent user to level the resource.

Hi Barry,
P6 use cost to weight WBS and or activities. There a lot of ways of doing it and the best practice is to use budget cost against its WBS and Activities with equivalent Cost Account which is very useful especially for Earned Value Management.
For this exercise if you wanted to weight your WBS/Activities using your own parameter like what you mentioned on the other post.
Example (just for this exercise) say $1000.00
Design -> 10% = $100
Procurement -> 15% = $150
Project Management -> 20% = $200
Construction -> 55% = $550
Total ->100% = $1000

The general idea is to know the value of each WBS that equivalent to the Budgeted Cost At Completion (BAC) that need to distribute for each activity.
On the other thread I mention on how to weight activities using duration if BAC is not available using 3 different options.
For this exercise I would like to use resource loading instead of expenses and or activity status fields.
1)     First create a resource for each WBS so BAC allocated cost can easily distribute with max unit/time = 1 (i.e. Labor)
Ex: Design, Procurement, PM and Construction
2)     Assign resource by highlighting all activities per WBS (i.e. Design WBS) then right click -> Assign-> Resources then double click Design Resource
3)     Repeat until all WBS activities have their own resources
4)     Show the Budgeted Labor Unit column by right click on the activity area window and select column->Unit-> Budgeted Labor Units
5)     On each WBS summary band will have a total number of units based on duration. (i.e. Design = 200 labor units) Use the WBS total unit to get the rates of each resource assigned. (e.g. Design = $100/200 hr or unit = $0.50)
6)     Select Enterprise-> Resources and enter the rate per each resource based on the derived rates per resource.
7)     Show the Budgeted Labor Cost column by right click on the activity area window and select column->Cost-> Budgeted Labor Cost
8)     Check the main summary band if equivalent to $1000.00 and each WBS cost = allocated cost.
9)     If everything is fine and according to what expected… CONGRATULATION!!! You weighted your WBS and Activities successfully.