Minimum Date Calculation (Formula)

Minimum Date Calculation (Formula)

I have three date fields in my form and would like to include a formula that calculates the minimum date of all of these fields.  Is this possible?  Some of  these fields may have null values.

e.g.

Due Date #1: 05/01/10
Due Date #2: 06/01/10
Due Date #3: Null

Formula = 05/01/10