Macro runs only if no blank cells

Hi,

Hopefully someone can help me. I've just started trying to do some real macro work and I'm stuck

I have a user form with a submit button that writes the data to a second sheet. This works great. What I'm trying to do is find a way to add to the macro so that it won't submit if any of the fields in the form are blank.

This is probably really easy, but I just can't find an answer.

Thanks!!