Loop through cells compare values add and move to another sheet

I am trying to allocate products from different suppliers to customers. For this I have an algorithm that I am trying to implement in excel. What I am trying is to place data from sheet data gathering allocation to ProposedTerm sheet. What I am trying to achieve is the following.
We have 4 cases but they all require the same procedure.
1- Same supplier can give same product description
2- Same supplier can give different product descriptions
3- Different suppliers can give same product description. We allocate product descriptions starting from first supplier and when capacity is finished we switch to other supplier capacity. In this case customer may get product from more than 1 supplier. Look at example workbook please in ProposedTermSheet.
4- Different suppliers can give different product descriptions

I think I need a loop that checks each cell in range for same product descriptions in DataGatheringAllocation sheet in column d. If exists than the sum of their total capacity in column L must be placed in ProductDescription Sheet j4:j along with their respective Product Names, KG/PCs

1. Data from DataGatheringAllocationSheet column c9 (Product Names)till end of activecell to ProposedTermSheet column e4 till down.
2. Data from DataGatheringAllocationSheet column d9 (Product Description)till end of activecell to ProposedTermSheet column f4 till down.
3. Data from DataGatheringAllocationSheet column e9 (Supplier) till end of activecell to ProposedTermSheet column d4 till down.
4. Data from DataGatheringAllocationSheet column f9 (KG/PCs)till end of activecell to ProposedTermSheet column h4 till down.
5. Data from DataGatheringAllocationSheet column L9 (Tot.Supply Capacity) till end of activecell to ProposedTermSheet column j4 till down.

Each cell in ProposedTermSheet represents a supplier and its product description from DatGatheringAllocation sheet. To begin with we need total supply capacity of that product description in column j4 in Proposed term sheet. Once product is allocated to customer, cellJ5 = J4-O4 (allocated amount to customer ). Allocated amount is taken from the ProductAllocation sheet, user enters demand of each customer manually in (ProductAllocationSheet) column I3, M3, Q3, U3, Y3, AC3 (Always offset 4 columns to right) for each product description. The customer information is copied to proposed term sheet in column N transposed.
My explanation may not be very clear but once you look at the example sheet I think you will understand what I mean. I did color coding for it to be easy read. Looking forward for valuable help.
Thank you very much.