Splitting out Excel data to multiple files based on one column's values

I have a large data set which I have to split out to multiple excel spreadsheets, based on the value in one of the columns. Say for example column D is the identifier, a company ID . I have multiple rows with the same company ID but thousands of different company IDs. The code should find all the rows containing each company ID, create a separate file for each company, and write into each file only the data corresponding to that company.

The master spreasheet would look like this:

Company ID Order date Quantity
1 5/1/2011 1000
1 5/5/2011 1500
3 6/1/2010 100
6 7/1/2011 5000
1 7/7/2011 500

File "1.xls" would look like this:
Order date Quantity
5/1/2011 1000
5/5/2011 1500
7/7/2011 500

File "3.xls" would look like this:
Order date Quantity
6/1/2010 100

File "6.xls" would look like this:
Order date Quantity
7/1/2011 5000

I hope I was clear enough. Thanks in advance for the help!