execute job in sql

Hi,
I am running this query from my database.
@PackageName varchar(100)

set @Packagename = 'JobName'
EXEC msdb..sp_start_job @job_name = @PackageName

In the query analyser of my database, I log in as a user with password.
This user has User mapping to my database and msdb with db_ddlAdmin
When I try to execute this query, the error I get is:
The specified @job_name ('JobName') does not exist.
BUT, if I log in as windows login, then this query runs successfully.
Do you know why please?
Thanks

let the account member of the following roles in user mapping of MSDB database:
SQLAgentUserRole
SQLAgentReaderRole
SQLAgentOperatorRole

Solved.
Thank you

[quote user="arkiboys"]Solved.[/quote]
Can you share your knowledge .

[quote user="arkiboys"]Solved.
Thank you[/quote]
Good to know it is solved. But when you share how you have solved it, it will be helpful for other readers to solve the same problem.