Crystal Reports SQL sep instance databases connection

Message

   I am trying to retrieve data from a seperate instance of SQL using 

Select * From MyRemoteServer.DatabaseName.dbo.Sysobjects eg
Select * From RFF-03\KRONOS.tkcsdb.dbo.DG_DailyReports

My server name is RFF-03 and the instance is KRONOS and SQL doesn't like the '-'.  If I use the server number 174.173etc, then it doesn't like the '.'

Does anyone know how to do this?

Debbie