Can I connect two Mac Pro to one monitor? I am using an apple thunderbolt display and two mac pro's.  I would like to connect the two processors to the one display.  is this possible?
No, you cannot physically connect both Mac Pro's to the same Apple Thunderbolt Display. However, you might look in to a KVM switch which lets one display connect to multiple computers. 

However, you could connect one Mac Pro to the display, and use Remote Desktop software on that Mac Pro to display the screen from the other Mac Pro.