Using combo box(s) to create a query

I have a two part question as follows:

1st part:
I am wanting to create a query that is driven by the user selecting a
value from a combo box on a form.

the combo box on the form is called "TypeofIssueID" and it's control
source is "TypeofIssueID" in a table called"tblEngineering".

it would be nice if when the user selects the value he wants to query
from the combo box the query is automatically generated at that point.
the user wouldn't have to select a "do this now" button.

2nd part:
the second part to this would be adding more than one combo box that a
user would use to select a query. How do I add more than one combo
box to generate the query? The query, like above, would run after the
user selected the last value in the last combo box.

How can I do this?

thanks in advance to all;

chris