displaying multiple tags on chart

Hi,

i have a table with coloums date/time, tagval ,tagindex. i can display a linechart with tagval(y-axis) and date/time(x-axis) by passing tagindex as a parameter at runtime to the query template.Each time the tagindex change,graph in the chart will also change,new tag with tagval and date columns will replace the old one.

My requirement is i want to show the tag for the past tagindex and present tagindex.with one column how can i display multiple tags simultaneously.

please help me.

points will be awarded for the feasible solution.