The error is to do with variable locking, so I would use explicit locking in code, and avoid the variable lock lists in the editor. Some notes about it here - http://wiki.sqlis.com/default.aspx/SQLISWiki/0xC001404D.html As an aside to increment a variable, you could use a second variable, which is set as EvaluateAsExpression and with an expression along the lines of DATEADD("d", 1, @[User:ateTimeVar]), so this second variable becomes value of the primary variable +1 day. It depends on exactly what you want to increment by and how.