How to add remove tag functionality in new plugin(remove tag from source)

Currrently i created new plugin for adding the new button In tool bar. now i am able to add new button in CKEditor.

if you will observe bold, italic button functionality then you will find that if i will select some text and then click on bold button then bold tag will come surround the text and if again i will select same text and again i will click on same button then that tag will removed from source.

so same functionality i want to implement in my case. currently i am able to add tag surrounding the text area but not able to remove..

so i want to add same bold type functionality in my case.. so please some one suggest me. how to add this functionality and what should i do for adding this functionality?????

i am creating button for <no-Lexicon></no-Lexicon> tag.