Delete lines in richtextbox that fall under the condition

Question

Using this link http://www.yellowpages.ca/search/?stype=si&what=sh&where=Ottawa,+ON&x=0&y=0 and telling HtmlAgilityPack to retrieve both address and place name at the same time ("//span[@class='listingTitle']|//div[@class='address']/text()[normalize-space(.)]"), I can get a list of placenames and addresses like this in a richtextbox:

1. jh ryder machinery limited
2. convenience storage ltd 3344 rideau
3. rd, gloucester, on, k1g3n4
4. kitchen interiors 146 colonnade rd,
5. nepean, on, k2e7y1

The first line is bad, it doesnt have an address. Line 2 and 4 are good, they have addresses. So what I could do is:

Check each line,

if the following line doesnt contain "numbers + ON" then delete line.

This will leave me with PlaceNames followed by addresses, which I will then split every other line into a new textbox, (so I have one textbox with placenames, and another with addresses).

I hope I made myself clear.

-Dd,