Custom report multi-select stor proc problem

Hi:

We have a new custom report (infomaker) that we want to be able to select multiple solicitors from a drop down in the report.  In the where clause of the stored procedure, I have a function to remove both single and double quotes from the passed variable (@solicitor), but I am getting a syntax error.  I get the same error when I use the charindex string (see eamples and errors below).

where 

dbo.lfn_matchparm(ISNULL(@solicitor,''), tsol.solicitor)>0) and tsol.campaign_no in (select campaign_no from t_campaign where category = 32 and fyear = @fyear)

Error:

Msg 102, Level 15, State 1, Procedure LRP_TDO_Solicitation_Goals, Line 202

Incorrect syntax near ')'.

Msg 156, Level 15, State 1, Procedure LRP_TDO_Solicitation_Goals, Line 204

Incorrect syntax near the keyword 'GROUP'.

With charindex:

where

tsol.solicitor in (charindex(',' + convert(varchar, solicitor) + ',' , ',' + @solicitor + ',') > 0)  and tsol.campaign_no in (select campaign_no from t_campaign where category = 32 and fyear = @fyear)

Error:

Msg 102, Level 15, State 1, Procedure LRP_TDO_Solicitation_Goals, Line 202

Incorrect syntax near '>'.

Msg 156, Level 15, State 1, Procedure LRP_TDO_Solicitation_Goals, Line 204

Incorrect syntax near the keyword 'GROUP'.

Any suggestions?

-James