Is it possible to have a field with a value list that is created by the data that is entered into that field?

For example, I live in an area that has very unique street names. I do not want to have to enter every single street name in order to "equalize" the way that the information is entered.

Can I create a field called "street" that allows me to see a pull down menu of the streets entered or add a new entry (which would then be added to the value list)?

This should probably be easy, but I just can't get my head wrapped around this concept.

Just define a value list to use values from the field itself. Then, as you add items to the field, they automatically get added to the value list. You can add an "other" option to the popup menu so that you can add new items, or if you are using a popup list, then you can click out of the list and enter new items directly into the field. Either way, they become part of the value list.