How do I change the properly change a Database in Unity Scene?

Hello,

I am using Unity with Vuforia and would like to click a button or tap on the screen to switch Databases/Model Targets. How can I programmatically do that?

For example, I want to switch from mt1.png to mt2.png (images attached) with a tap on the screen, including switching the Guideview. They are from different databases and have different model targets and guideviews. 

Any help will be greatly appreciated. Thank you!!