General :: Adding Values (Multiple Entries) In One Field

I have a field named Supplies Expense. As an analyst inputs a business's expenses, it may require multiple entries into this one field. What is the best way to accomplish this?

For example:

Supplies Expense (Field Name) [$0.00]

The analyst has the following data:

2009 Financial Statement
Paper $50
Depreciation Expense N/A
Ink $100

So, going down the list, the analyst goes into access and enters $50 for paper then later needs to enter $100 for ink.

What is the best way to combine these multiple entries into a single Supplies Expense field and allow for a quality check of the individual numbers at the end of the project?