Help Box in Userform Testing

Good morning all,

I am trying to see if it is possible to create a populating help box on a userform.

Attached is a mock up file to test it on, what I am looking at accomplishing is when a user has selected a textbox or other - (either by clicking or tabbing), when the focus is on that box a help prompt is filled out in the large "TextBox4".
I have created a "Help" Tab reference and column "B" is the wording I am wanting to appear.

Simply:

When a user has selected the TextBox1 (Next to "A") = in "TextBox4" appears the wording "Need to enter a time. Eg. "12:00""

The trick is to show when the focus is on the Textboxes or others...