schtasks.exe doesn't have any command-line capability for passing arguments into the scheduled task. One possible way to do it is to save the argument text in a (temporary) bat file of its own with contents specially crafted to set it as an environment variable. Then all you have to do is call the argument bat file from the scheduled task bat file and the environment variable will be set.
The contents of argument bat file would look like:
set parm=ParameterToPass2
The contents of your scheduled task bat file would then execute the argument bat file:
C:\wherever\argument.bat