You can create a repeating div region within Dreamweaver pretty much the same way you create a repeating row region in a table, first you add the content you want to repeat, a div in this case, then select that content, again, the div and add repeat region to the selection by going to the Server Behaviors panel, clicking the + button and selecting Repeat Region.
When it comes to counter, I've already supplied some sample code, but I'll try to explain again...basically, you create a variable, set it's starting value, in this case 1, but it could be any value that is useful for the case at hand, and then within the repeat region, you increment that variable value (add one to the current value).
If you need to do something with the value as you loop (repeat), then check that value, either before the increment or after the increment, depending on exactly what you want to accomplish. In this case it checks the remainder of the division of the counter by 2, if that remainder is 0, then we have an even row, then you can do whatever you want to based upon the result of the check against the current value of the counter, in this case write out the page break div, but you can do other things, such as write out a CSS class name for the alternate rows.
You can read up on how to apply repeat regions in the "Making pages dynamic" section of the Dreamweaver help. As for counter variables, I'm not aware of anything in particular that discusses the topic. A casual search of Google for PHP counter variable yeilds a few results, perhaps start there.
