Query Based on Form with Multiple Criteria

[Nan]

I have created a form to update a query which then runs a
report using "Create a Form to Enter Report Critera"
which I found on the Access help section.
What if there are multiple text boxes on the form but
not all of them may be used each time the report is run.
For example I have six possible criteria but I may only
want to choose three and leave the rest blank. How do
you tell the query to ignore the text boxes that have
been left blank?

Thank you.