How to open a particular page in chm file using c#

Question

Hi, I am working in a c# desktop application.I want to open a particular page in the CHM file when the user pressed F1 key according to the opened form. Eg. When a user is in a Form Purchase Order then when he presses F1 key then the help page of the form Purchase Order should open directly. How can I get the desired operation? Rajesh