how can you draw lines form one point to another

hi! can somebody help i am doing  a certain project which requires me to draw  lines from one point which its co ordinates are in two text box   to other point of which it also has co ordinates defined on a textbox.This lines must make a closed triangle with the last co ordinates are also defined on a textbox.
 can you please also provide me with exampes , i will be much happy if you can also email me the answer at:[email protected] PLEASE HELP ME!

AND! I apologise, my english is not good but i've tried to make it clear.
 another thing i forget to specify i'm using vb.net