Firstly, your data design is flawed. Rather than having 6 networks/roles in the user account, these should be in a related table. What happens is there is 7 or 8 or 100 networks?
But to reply to your specific query,
bodytext = bodytext & iif(len(me.network1 &'')>0, me.network1 &', ','') & iif(len((me.network2 &'')>0, me.network2 &', ','') & ........
NB All the above quotes are single quotes, not double.