First when adding the contents of any type of file make sure to surround it with My file data here so that it shows up like this:
[MACHINES] REMEXEC0=c:\progra~1\intern~1\iexplore.exe http://www.google.com/
Now to answer you question. REMEXEC commands by default wait for the process to terminate. If you want it to not wait, use the ASYNC at the end after a comma:
[MACHINES] REMEXEC0=c:\progra~1\intern~1\iexplore.exe http://www.google.com/, ASYNC
Thank you, this worked perfectly!
It should be noted that you are probably launching internet explorer as the Local System account.
This doesn't really matter if the users are local administrators. However, if you intend to lock them down, you may be providing them with an internet explore process running with full permission on the workstation.
To resolve this use the StartAsUser.exe. If you are on 8.7 (maybe you need a service pack or not I am unsure), it should be on your agent workstation already. If not you can download it first.
[MACHINES] REMEXEC0=</qt>%LDMS_CLIENT_DIR%\StartAsUser.exe</qt> c:\progra~1\intern~1\iexplore.exe http://www.google.com/, ASYNC