Yes, I wrote everything with the exception of the syntax highlighting edit box. Actually the parsing for a BAT style program is so simple, each line starts with a command (or a colon for a label or comment) it can't start with anything else. You don't have assignment in the same manner as you do in "real" programming languages. With the exception of the IF statement and the FOR loop each line is a complete statement.
I've written much more complex compilers than this. ScriptBrix for example use a VB-like language, allow you to create classes and instanciate objects and so on. This in comparison was a piece of cake and only took me about two days to write (with the exception of the help documentation).