Visual C# 2010 Winforms

The topic title is pretty self explanatory.  I want to create a method that will count the total amount of money deposited and return the number of lines in a rich text box.  I need a method that can be implemented in plain code and inside its own function.

I am combining this with another method I have to get a list of commands, which should be easier than using a dictionary array/collection.

Any help is appreciated.  Thanks.