If anyone is as obsessed with their child's growth as I am you may be interested in this software which is available from the Centers for Disease Control website.  The software is called Epi Info 2000 and it is mainly for investigating disease outbreaks and that type of thing.  But it also has a module to track children's growth.  You enter your child's date of birth and measurements and it will tell you what percentile your child falls into and you can track it over time and even print out a pretty growth chart.  If you were really good at computer stuff you could even modify the form to include lab test results and dosage changes but I haven't figured that out yet.

The website to download the software is: http://www.cdc.gov/epiinfo/EI2kmanl.htm

It's easy to use but a little confusing.  If you need help feel free to e-mail me and I will try to help.