Problem running stored procedure

[eRTIS SQL]

hi,

I want to use a stored procedure inside a stored procedure simulteanously changing the database.
this is my base store procedure

alter PROCEDURE create_file @dbname sysname
AS
declare @fname varchar(30)
declare @fsizes nvarchar
BEGIN
DECLARE @cmd varchar(1000)
set @cmd = 'osql -E -d ' + @dbname + ' -Q "exec ret_sizes @fname OUTPUT,@fsizes OUTPUT"'
exec master..xp_cmds hell @cmd
END


if i execute the his "exec create_file ertis"
i get error as

Msg 137, Level 15, State 2, Server HCC-BPVHD1, Line 1
Must declare the variable '@fname'.
NULL


the procedure called inside the mail procedure is

alter procedure ret_sizes
@fname varchar(30) OUTPUT,
@fsizes nvarchar OUTPUT
as
begin
select @fname=name, @fsizes=size from sysfiles
order by fileid
end


Please help me and not why it is getting eror.