Help! Which formula is best to use?

[rows and columns]

Hi everyone. I am a beginning in excel and need help. I have to distribute 2684 sales to a number of customers. Based on a simulation, I now have 1220 customers who account for these 2684 sales (see screenshot). I have also their customer ID. My task is now to use this distribution to allocate the customers ID on the sales sheet (see screenshot). I tried using Index Match function but I keep getting N/A. Any help is greatly appreciated!

 

[SunnyAlv]

May I know your index matching formula? And where is the primary key for the index? its a number in Column A?

 

[rows and columns]

May I know your index matching formula? And where is the primary key for the index? its a number in Column A?

This is the formula I tried to use INDEX(Distribution!$B2:$B2685; MATCH(ROW() - ROW($D1); Distribution!$C$2:$C$2685; 0)), but now I realize that it does not really help me in allocating the customers ID on the sales sheet correctly. The idea of the task is that if a Customer ID has 4 purchases, then that Customer ID should appear 4 times in the Sales database. But I guess I am having troubles understanding how to allocate each ID to a specific purchase in the sales sheet, i.e. to a specific receipt, rather than to a random purchase.
What do you mean by "primary key for the index"? As I mentioned, I am truly a beginner so there is a lot I don´t know haha

 

[rows and columns]

I actually think I need to use VBA..anyone able to help with the code?

 

[mumps]

It is hard to work with pictures. Also, your data in the second picture doesn't contain any ID's. It would be easier to help if you could use the XL2BB add-in (icon in the menu) to attach the desired selected range (not a picture) of your data. Alternately, you could upload a copy of your file to a free site such as www.box.com or www.dropbox.com. Once you do that, mark it for 'Sharing' and you will be given a link to the file that you can post here. Explain in detail what you want to do referring to specific cells, rows, columns and sheets using a few examples from your data (de-sensitized if necessary).