Software install dependent on a configuration.

Software install dependent on a configuration.

Hi everybody, 
My organization is changing Anti-Virus Vendors and we need to do the following. 
1) Uninstall the current anti-virus Software.
2) Reboot 
3) Install the new anti-virus software.
4) Reboot 
Because it's anti-virus software, I can't have any real break between when we uninstall the current software and install the new software. 

I am successful in uninstalling the antivirus software through a custom script . And I'm successful in installing the software, but I can't figure out how to link these two events together. 

Thanks 

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