I tried that, but it doesn't work.
I think the problem I'm having is that I can't run that line before clicking the online button in Genesis, otherwise it's trying to mount the share before it gets online and fails.
I need to run that line once I've clicked the online button in genesis.
It's been a long time since I used Genesis so I can't remember how to automatically start it from user-startup, but that's what you need to do.
To create a script that launches from an icon, put the smbfs line in a text file then make sure it has the Script protection bit set and create an icon that uses IconX as it's default tool.
I'm not in front of an Amiga at the moment otherwise I'd give you more detailed steps.