Yes, it's possible. You'll need to have global variables set up in your DTS package and use the DTSRUN utility to pass values to those global variables Look up "dtsrun utility" in the SQL Server books online for information on the command line switches, especially the /A argument, where you'll have to include the global variable name and a number that represents it's data type.
From a stored procedure, you can execute xp_cmdshell to run a DTSRUN command.
Here's an example. My global variables are named strFirstName, strLastName, and intEmployeeID
xp_cmdshell 'DTSRUN /S "Name of your SQL Server" /N "Name of Your DTS package" /A "strFirstName:8=Bob" /A "strLastName:8=Smith" /A "intEmployeeID:22=99" /E'