[RESOLVED] how to load files in richtextbox1 with combo1 selection

Please help how can i load .rtf file in richtextbox1 with combo1.
e.g. in combo1 I have 5 different subjects like Science, Math, History, Economics, English
and i want when user select Science from the list of combo1, then it load rtf file from path "D:\vb\Science.rtf" and so on
Please help, how can i do it.

Thanks in advance.