"Syntax Highlighting", if you will...

I am making a program that has its own little syntax highlighting thing. For example, I have:

VB Code:

if workSpace.Text.StartsWith("<>") then
workSpace.ForeColor = Color.Blue
end if

Now that works all fine and dandy, but when I erase the <> the text color stays blue.

Should I use an else statement here?
Does anyone have any solutions?

I also need to know how do I access the different lines of the richtextbox (workSpace), EXAMPLE:
If I want the font to be blue if <> is on the first line. But, if I press enter, it will be black again, so I could add a different syntax than <>, such as @> or !>, ect ect ect.

*this is not a Java, C++, Ruby, or any other programming language editor*