Software Deployment

Hi

I've a created an administrative install for a in-house-app.
I did this with msiexec /a mymsi.msi TARGETDIR=\\Server\Installs\Myapp
On a client I then did msiexec /i \\Server\Installs\Myapp\MyMsi.msi
Later I patched my source with msiexec /a \\Server\Installs\Myapp\MyMsi.msi /p C:\temp\Mypatch.msp

Now here is what I would like to know. Is it possible to re-install myapp with /f to get the new files.
I've tried msiexec /fav \\Server\Installs\Myapp\MyMsi.msi on the client where it already is installed. The new files will not be installed.
Must I first remove my app and then install it again?
I know I can install the Mypatch.msp separately on the client. I just would like to know if there is a shorter way.