Reading last lines from QTextEdit Document

Hi I have a QtextEdit control, in which a user can type in text, what I want to do is read the last 100 lines of text that has been entered.
i.e. whenever the user presses the [ENTER] key, I want to read/get the last 100 lines of text from the bottom of the QTextEdit control.
Any suggestions on reading from the bottom of the QtextDocument?

you split the text at the new line in a stringlist and the function size()
shows you the number of lines, then you can read the last 100 lines.