It may appear a couple times... but Yes... so it appears it already forwards the querystring from the current page to the next.
You can just make sure the querystring is on the current page, or add it in front like:
<param name="movie" value="../DynamicWebCharts/open-flash-chart.swf?data=../DynamicWebCharts/Data/mypage_dataparser.asp?cTag=opcLab-19&<%=Request.QueryString()%>" />