capture checkbox values

Preface: I am new to JavaScript and I know nothing about this language.

I need some JavaScript code for the following: I created a form with 8 checkboxes and a submit button.  If the boxes are checked, I want to populate the address field of an email (w/ one or multiple addresses). For example: if Child Care and Sound Tech are checked, the email address field should be populated with Childcare@test.com; Soundtech@abc.com. If nothing is checked, prompt with an error msg.  Moreover, I want the email sent in the background without the user having to click the send button.

Your assistance is appreciated

BrendaHC