Conversion of data

I know someone out has the answer to this simple question. Is there a way to convert Lat/Long data to MGRS (Military Grid Refrence System) in Excel? If so, is this a function or a conversion? I am a US Army pilot and get my data as Lat/long but need to convert it to MGRS to be useful. I would do this on my pocket pc or pocket calculator if it were possible, I just need to know the formula to convert the numbers. By the way, the Lat/long data I get is extremly accurate so don't skimp on the output. In other words, some lat/long conversions in Java format will only convert upto 4 places per direction.

Thanks