reporting services - Subreport visibility based on field and parameters -

i have main page many subreports dependent on client parameter don't want pages show. have dataset 'params' indicate if each subreprt should visible fot client picked based on 1 or 0 in field of name of report.

i used below had error hadn't used aggregate

=iif(fields!clientname.value,"params") = parameters!client.value , (fields!overview.value,"params") = "1" , true, false 

i added in first around fields @ first client in params table. want correct subreports visable based on client chosen in parameter