I can't solve this problem, which should be absurdly easy.

I need to design a line chart with time in x and drawing two values. I get my data from an xml file, but I need to be able to load the values from parameters. I had to use formulas to display the two values I needed to show, because it wouldn't let me summarize otherwise.

I create the parameters with the same data type. I go to the Selection Expert, choose the field, select "is equal to" and choose the parameter. When I refresh the report, I'm asked to enter the values. I type groups of three, five, ten, but the chart doesn't show. It goes blank. Has this happened to anybody else?