table with column summing up from 2 different datasource

[Lily]

I'm having issues with trying to add column that will perform arithmetic using info from 2 different tables with different datasources...

And because I need to expand upon info in the field.  I don't think I can put in simple arithmetic using the textboxes.. but I can't select the field from the other table... so how can I do this?  I attached a pic explaining it...

 

Please help?

[Lily]

I figured it out.  I ended up setting up a new parameter then attached the datasource for that field then in the 2nd table where I used the parameter in my equation