I can see you were given all the info in a thread last year but the old application form was very off putting which is probably what you mean when you say they wanted a mothers name (which of course you don't have)
Go to this page on Irishgenealogy
http://www.rootschat.com/links/01j6t/ Choose option 1. (photocopy for genealogy and research purposes) and download the new form which is especially for genealogy.
You just need to fill in the form and post to the address on the top. They can email the cert back to you.
Payment is 4 euro and they ask you to supply your credit card details - I don't like doing that so usually place a note with my phone number and ask them to phone me for my payment details - they don't seem to mind that.
Here are the details you need to fill in on the form regarding his birth details in Tullamore from the index.
1. Birth
2. Robert Mills
3.(leave this blank)
4. Year - 1923
Quarter - 2
Volume - 3
Page - 431
Once you get your grandparents names from that cert you will be able to get their marriage cert free on IrishGenealogy.ie and if you have any problems at all then just shout, we are here to help
