Activate a UserForm by Right Clicking a Cell

Hello All,

I'm not sure if this is actually possible without some sort of 'Add-In' but I thought I would ask anyway!
I have created a UserForm which I want to open when the user 'right clicks' a specific cell (for example, H8).
I have already been able to do it if the user left clicks on the cell by putting a code on the sheet, but this causes problems.
A right click utility would work perfectly I am sure.

Regards,

Stuart