Hi Stefan,
I created a small program that can be used to open a CHM file with a keyword from EmEditor external tools.
Please download
http://www.emeditor.com/pub/eehelptool.zip
You can specify external tool properties as:
Command: the path to eehelptool.exe
Arguments: “CHM file path” $(WordText)
Please see the screenshot included in the zip file.
I hope this tool helps you.
Thanks!