I'm trying to execute simple SQL Server stored procedure from Powerbuilder 9 development environment. The output parameter returns 0 to Powerbuilder, it is not what I was expecting
Stored procedure is:

create procedure manta_sequence_proc
@sequence_name varchar(30),
@sequence_id numeric(19,9) OUTPUT
as
begin

SET NOCOUNT ON
Begin Tran seq
update manta_squrence set sequence_id=sequence_id+1 where sequence_name = @sequence_name

Commit Tran seq
select @sequence_id = sequence_id from manta_sequence where sequence_name = @sequence_name

-- print 'name' + @sequence_name
-- print 'id' + str(@sequence_id)

SET NOCOUNT OFF /* Enable all rows affected messages */

return @sequence_id

END
go

The call from Powerbuilder is:
long ll_sequence_id
string ls_sequence_name

ls_sequence_name = 'TEST'

declare manta_sequence procedure for manta_sequence_proc
@sequence_name = :ls_sequence_name,
@sequence_id = :ll_sequence_id output;
exec manta_sequence;

MessageBox('test', string (ll_sequence_id))
// this returns 0 and it should some other numer

Can anyone help, I'm new to Sql Server.
Thanks in advance