SQL: Update or ISNULL function or CASE or SSRS Expression

Hi guys - I have a scenario below. 

Select letterid, patientid,applicationid, mcpsreceived, letterrequestdatetime from letterrequesthistory

where patientid = 77203
and letterid = 139

I have an expression in SSRS report like this 
=iif(Fields!McpsReceived.Value = "N","x","") -- This means if the MCPSreceived value is N, then it will create cross 'x' symbol. I am using this 'x' for a check box. 
Below is the check box 


When I executed the report for this patient, the report is pickup the patient with value 'X' (applicationID 75397). 
My question is if the same patient has value "N" and "X" on the same Letterrequestdatetime, I want to to show 'x' symbol. Is it something we can create or update an expression ? Or some thing like ISNULL function or case statement in the select query ? 

Thank you