Reading a Sum(field) column in RPGSQLLE

[Jonathan Mason <jonathan.mason@xxxxxxxxxxxxxxxx>]

I am trying to total a an amount on a number of records in a file within 
an RPG program using embedded SQL.

I am building up the SQL statement using:

C* Build the SQL Statement for the current line...                   
C                   Eval      wSql = 'select sum(' + %Trim(CAENVN) + 
C                               ') into ? from ' + %Trim(CAEMVN)     
                                                                    
C* If selection criteria was passed and it isn't *NONE then add it to
C* the SQL statement...                                              
C                   If        CAAGNC <> *Blanks and CAAGNC <> '*NONE'
C                   Eval      wSql = %Trim(wSql) + ' where ' + CAAGNC
C                   EndIf                                            

And then preparing and running it using:

C* Now execute the SQL statement...
C/Exec SQL                         
C+ Prepare prpSQL from :wSQL       
C/End-Exec                         
                                  
C/Exec SQL                         
C+ Execute prpSQL using :wTotal    
C/End-Exec                         

However, I am getting an error in the joblog that says:

Token ? was not valid. Valid tokens: : <IDENTIFIER>.

Can anybody tell me what I'm doing wrong?  I thought I had to use 
parameter markers for the variable name.

Thanks

Jonathan