Have a look at 
Select a Startup Device and to boot from USB you'll need to use the Plop Boot Manager 5.0.
Other options are to add the following to the Virtual Machine's .vmx configuration file.
bios.bootDelay = "3000"
bios.forceSetupOnce = "TRUE"
Have a look at: Editing the .vmx file for your Fusion virtual machine (1014782)
Note the above link might give a Gateway Timeout as it looks like VMware is having troubles at the moment.
Message was edited by: WoodyZ