SSIS : Using Windows Environment Var's In Stored Procedures ..

Hi,

I have a small requirement because of which i am facing some migration problems.
For changing the variables say InitialCatalog and Custom logging destination path, i am making use of XML configuration files. Till here i have no issues.
But problem starts here. Basically DTS package is called by calling a stored procedure from a front end application.
Within the stored procedure the package location say (D:Packages<packagename.dtsx>) is being hard coded due to which i need to change the package
location paths each time when i am migrating the stored procedures to Testing and Production environments.

Is there any efficient way of avoiding the hard coding of the package paths using Windows Environment vars or something else.
If so please help me out.
Any help would be greatly appreciated.

create procedure spexecDTS_Pkg
@g_p1 varchar(50),
@g_p2 varchar(50)
AS
declare @jid uniqueidentifier
declare @cmd varchar(4000)

SET @cmd = '"C:Program FilesMicrosoft SQL Server90DTSBinnDTExec.exe" /F "D:Packages est.dtsx" '
SET @cmd = @cmd + ' /SET "Package.Variables[User::userid].Properties[Value]";'+'"'+@g_p1+'"'
SET @cmd = @cmd + ' /SET "Package.Variables[User::cname].Properties[Value]";'+'"'+@g_p2+'"'

DECLARE @jname varchar(128)
SET @jname = cast(newid() as char(36))

-- Create job
exec msdb.dbo.sp_add_job
@job_name = @jname,
@enabled = 1,
@category_name = 'Samples',
@delete_level = 1,
@job_id = @jid OUTPUT

exec msdb.dbo.sp_add_jobserver
@job_id = @jid,
@server_name = '(local)'

exec msdb.dbo.sp_add_jobstep
@job_id = @jid,
@step_name = 'Execute DTS',
@subsystem = 'CMDEXEC',
@command = @cmd

-- Start job
exec msdb.dbo.sp_start_job
@job_id = @jid


Thanks in advance.