Problem In Calling A Stored Proc With OUTPUT Parms

I have a problem in calling a procedure.
It has two input parameters and seven(7) output parms.

When I run it this way:

exec usp_List_Relationship_Users @relationship_id = 1851 ,
@status = 'Channel Member',
@cust_idOUTPUT,
@user_login_id OUTPUT,
@username OUTPUT,
@password OUTPUT,
@status_id OUTPUT,
@sdesc OUTPUT,
@administrator OUTPUT

I get this error:
Server: Msg 119, Level 15, State 1, Line 10
Must pass parameter number 3 and subsequent parameters as '@name = value'. After the form '@name = value' has been used, all subsequent parameters must be passed in the form '@name = value'.

But when I run it this way :
exec usp_List_Relationship_Users 1851 ,
'Channel Member',
@cust_idOUTPUT,
@user_login_id OUTPUT,
@username OUTPUT,
@password OUTPUT,
@status_id OUTPUT,
@sdesc OUTPUT,
@administrator OUTPUT

I get the expected results. Why should I omit the name of the name of the input parameters? I don't know why I am getting this error if don't run by ommitting the name of the input params.

Any help regarding this matter is greatlt appreciated.
You can assume that all the variables are declared prior to executing the stored procedure.

Regards
Sushruth Nanduri.