Yes you can just open the help file and let the user find their way to the topic that relates to the screen they are in. The more helpful way is to provide context sensitive help so that if the user is in Screen A they get the help for Screen A and if they are in Screen B they get the help for Screen B.
That's the same for any help, not just CHMs.
See www.grainge.org for RoboHelp and Authoring tips
I fully do agree to the concept of context sensitive help.
Since I do not have a software developing back ground. I do want to understand as described below:
Help button is viewed irrespective of the page that is opened in an application. So without mapping every htm page to the respective page, How can a CHM file be integrated with the application to show the help.
I would like to add my two cents to this disscussion.
for Any SSL (output format) in RoboHelp, CSH is not generated untill you map the topic you want to use as CSH to the a map ID which is used by the developer of the application as CSH help.
In RoboHelp in the Project setup pod there is method to autocreate map ID with all the topic in the project or use another external heder to define your mapping.
you just need to do it once and gets picked up by any output format you generate.
Hope this will help
Have a look at these pages - http://www.grainge.org/pages/authoring/calling_webhelp/calling_webhelp.htm
they all talk about WebHelp, but the principles are the same for CHMs too.
So finally it does come down to mapping each topic irrespective of the output.
Thanks everyone, that sorts out my query.