WIS 10006 error: object does not exist in report...

Hello All,

I've been having trouble with this particular formula that i'm using as a variable for parent-child report linking:

 ="<a href=\"../../opendoc/openDocument.jsp?iDocID=AVMeLBMmFrdJkNpCFp33vjs&sDocName=Open+Incident+Details+Report+-+Owning+Group&sIDType=CUID&sType=wid&sWindow=Same&lsSDateOpened-YearMonth="+[Date Opened - YearMonth]+"&lsSResolutionTimeCategorization="+[Resolution Time Categorization]+"&lsSOpCatTier1="+[Op Cat Tier 1]+"&lsSOwningGroup="+[Ticket Owner]+"\"target=\"_blank\">"+""+[Ticket Count]+"</a>"

The object in question is [Op Cat Tier 1]. This object is in query filter of the child report. All the other values pass from the parent to child report w/o issues but as soon as I add [Op Cat Tier 1], the error message appears:

The object '[Op Cat Tier 1]' at position 302 does not exist in the report. (Error: WIS 10006).

I've tried passing the value using both &lsS and &lsM and using 'in list' or 'equal to' in the child report. I've been struggling at this for a while. Any ideas?

Thanks,

Carter