Decode and escape characters help..

Hi everybody,
I have a little issue with a decode statement, I'm using Oracle 10, this is the query:

SELECT JOBEXE.OPS_FK
FROM VS_AM_REQUEST_ITEM JOBEXE
WHERE JOBEXE.JOB_KIND IN ( DECODE ( &value , 'REJ' , 'REPA' , 'PRJ', ' ''PREP''||,||''MAIN'' ' )) ;

Basically if value is PRJ then JOB_KIND can be equals to PREP or MAIN , so I tried to nest a decode into an in, but no rows are selected...
Thanks in advance for the help!