Counting the Occurance of a Root Number only

Hello all,

First, have to put out there that I am a newbie to posting on a help forum - but I have always found SO much useful advice and solutions here, that I thought I'd give this problem a go. There may be a solution out there, and I'm just not searching for it properly. Anyhow - here goes...

I am modifying a spreadsheet where I need to report on the number of orders that are received. However, for reasons I can't explain (the spreadsheet was set up in a way and I'm having issues changing their reasoning) - each line is an amendment of the root number. For example, an order with 4 items would be entered as follows:

IT13-ABC-0211 (1)
IT13-ABC-0211 (2)
IT13-ABC-0211 (3)
IT13-ABC-0211 (4)

I need to report on the total number of ITEMS ordered -which is easy. But, I also need to report on the number of ORDERS received. I have a summary sheet that does a Countif of items. How do I do a count of total orders received? Basically - how do I count the occurance of the "root number" just once - keeping in mind that the root number will change everytime an order with multiple items is received?

Alternatively - do you have a suggestion on how the order numbers could be entered and reported on to gather the same information (without creating a bunch of additonal cells in an already cumbersome spreadsheet?)

Thanks in advance!