Sumeet,
First you will need to move the selections from your drop down menu into a data source such as an XML file and link it as a secondary data source. To do that check out this thread:
http://infopathdev.com/forums/topic.asp?TOPIC_ID=1258 . After that is done, you can display your drop-down values as either a drop-down list or a repeating table. If you put a control on the view and link it to the same node that you pull the drop-down list values from you can easily add (or subtract) options from the drop-down. However, you might want to look into some kind of script or conditional formatting to keep users from deleting options that you do not want deleted.
Hope this helps!
---------------
Matt Faus
InfoPath Dev Texas
Matt Faus / Microsoft InfoPath MVPQdabra® Software / Streamline data gathering to turn process into knowledge