Getting a list of cms tables in a drop down in a section

Hi - I need to get a list of "sections" to display in a drop-down list in a section.  For example, I have a section called Main Nav which is a category section - I want to be able to allow the user to set this "page" on their site to be a listing page for a blog.  I need them to enter the name of the table they are getting the list records from.  Right now I have this as an entry field - I'd like it to be a selection list.  That selection list would have to show the names of the cms tables available for the listing WITHOUT the cms_ prefix on them.

How can I setup the list field properly to show the list of cms tables available?

Thanks in advance and I'm sorry if this question has already been answered - I searched the forum and couldn't find it.