Creating an extendable list of items

I need to provide a way for a user to create and extend a list of name-value pairs.  I.e. the display looks like a 2 column property grid, they can edit both the name and value of existing ones and also click an "add new argument" item in the last row to create a new one.  Kind of like how the menu editor in VS works where you get a "type here to add new item" and when you do that another "type here" appears below it. 

The output looks like a property grid, which I've used quite a bit, but the grids don't let you edit the caption, just the value.  Is there a way to do this?  Or is there a different control I should be using for something like this?

Thanks,

Rick