Need help making digital signature field read only if required fields are null

Using Adobe LiveCycle Designer, I have a digital signature field.  I want to prevent users from being able to digitally sign the pdf if any required fields in the pdf are null or blank.  I'm a newbie to scripting so any detailed help would be greatly appreciated.  The required fields in the pdf include radio buttons, check boxes, text field, etc.  I appreciate any help anyone can provide.

Thanks