Question : where case - parameteres

In reporting serives i have one parameter multivalue. I want the user type 'All '  appears all rows,
but i also want  type some values  '123213','2999', '345345'

then..my sql is :

  ... where (agrupador  IN(@OlapAgrupador)   OR  @OlapAgrupador ='All ' )...

this is ok when only i type one value or when i type 'All ', but when i type 2 values is error ("AN EXPRESSION NON-BOOLEAN TYPE ESPECIFIED IN A CONTEXT WHERE A CONDITION IS EXPECTED, NEAR ',')

when my sql is   only   : where agrupador  IN(@OlapAgrupador)   , this is all right.  (but i have not posibility 'All ')

Why not support multivalues (in)  ?

Answer : where case - parameteres

Swap it

  ... where (agrupador  IN(@OlapAgrupador)   OR  'All' IN (@OlapAgrupador) )...