USING LOOKUP FUNCTION IN CHART

Good Afternoon,

I have created a simple chart in SSRS that is sourced from Analysis Services. The Grouping is by Month and the values are just attendances per month.

I want to add a 2nd series to this chart using a stored procedure in SQL.

Both share the field Month and could be linked on that field.

Does anybody know how I can use the lookup function to add this field to my chart.

Thank you