How to find dates based on mathematical calculations

I have a excel sheet with three columns:

1. List of duplicate IDs of customers.
2. Amount spent by them in $.
3. Date of the spend.

The sheet is sorted on the 1st column i.e. List of duplicate ID's of customers. Every time a customer spends something it is recorded in the excel sheet with the ID, spent amount and date of spend.

What I want to extract is the 'ID'(1st column), 'Collective amount spend'(2nd column) and 'date' (3rd column) on which a particular customer has reached the cumulative spend of $500 for all those customers.

Can anyone help in how it can be done easily in MS excel?

**Customers**        **Amount**        **Date**
00000000001             $200           12/01/15
00000000001             $300           12/08/15
00000000001             $100           12/25/15
00000000002             $200           12/03/15
00000000002             $400           12/09/15
00000000003             $200           12/11/15
00000000003             $100           12/15/15

This is some sample data to simplify the question. I would like to get a sheet as follows:

**Customers**        **Amount**        **Date**
00000000001             $600           12/08/15
00000000002             $600           12/09/15

Let's say we are updating the data as follows:

**Customers**        **Amount**        **Date**
00000000001             $200           12/01/15
00000000001             $200           12/08/15
00000000001             $100           12/25/15
00000000002             $200           12/03/15
00000000002             $400           12/09/15
00000000002             $100           12/13/15
00000000003             $200           12/11/15
00000000003             $100           12/15/15

And the result we get back now should be as follows:

**Customers**        **Amount**        **Date**
00000000001             $500           12/25/15
00000000002             $700           12/09/15