Brijesh,

You can use an ISelectionFactory implementation on your property to set where possible values are driven from.

There's an example in the documentation here:

http://world.episerver.com/documentation/Items/Developers-Guide/Episerver-CMS/8/Content/Properties/Property-types/Single-or-multiple-list-options/

This example has some hard coded key/value pairs - and you can extend it to meet your requirement by storing the dictionary somewhere within Episerver. I'd recommend placing a property on the Start Page or a Settings Page that allows administrators to control these values. This could be a Content Area that allows Blocks to be placed within it to set potential values.

Once you have that property, modify the ISelectionFactory implementation to read the dictionary from it.

Hope this helps,

/Matt