Instead of Copy the msi to some other Location you can adjust the "Release Location", also in the LE Version.
Expand your InstallShield-Project, Got to "6 Prepare for Release"\Releases, select SingleImage and in the Build Tab adjust the "Release Location".
In my Case i used "<ISPROJECTFOLDER>..\Runtime" which creates the setup.exe in <projectdir>\Runtime\SingleImage\DiskImages\DISK1\setup.exe
To get rid of the SingleImage\DiskImages\DISK1 Stuff, you could add a dependent Project to your solution, and use the post-build events there.