Javascript: Drop down and check box. How can I make a drop down or check box write

Javascript: Drop down and check box. How can I make a drop down or check box write

to textbox? It is for a work project so I want to check all the boxes and then have it write to the text box so I can use it for our help desk tickets.

Example:

I could check these and
Checkbox: Customer not home
Checkbox: Customer wont be there until PM time frame.

Now it would write to a text box to say

Customer not home. Customer not available until PM time frame.

Any ideas? Thanks!