How to read the Notes/Text at runtime

Hi,

I am in opportunity screen and there is a notes field from BTText. I want to perform some operation in BADI_SAVE by comparing the current/new value which user has entered on screen with the text which is alreay saved in database tables(ST**).

For old value which is in database tables, I can use READ_TEXT FM and get the notes text. But my question is what FM/Method can I use to get the runtime value.

Lets say we have a opporutnity Opp0001 saved in database and the Notes text is "This is text".

Now I opened this opportunity and click on Edit.

I changed the notes text to "This is new text" and press "SAVE". Now in BADI_SAVE, I want to get compare both text - if it's different I need to append some text.

How can I read New value which is "This is new text" in BADI_SAVE.

Thanks,