Add entry to context menus

[BrightSoul]

Hi everybody,
I have to add an entry to the context menu that shows up when the user right-clicks a file. I'd like to do this in order to send that file to my application, not unlike the "Add to Zip" entry does with Winzip.

I wrote this value
myApp.exe "%1"
to this registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\txtfile\shell\My Entry\Command

and MyEntry is correctly displayed inside the context menu for txt files.

The problem is that this isn't working for a custom file extesion such as .qwe
If I write that same value to this key:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\qwefile\shell\My Entry\Command
MyEntry won't show up
Am I missing something?

Thanks for any follow-ups.
bye