There is the limit of one field per perameter, but you can have as many parameters as you want. You'll just get prompted for each parameter.
You can create a calculated field that concatenates your three existing fields - something like FullName=LastName&FirstName&MiddleName adding in any spaces and punctuationmarks. Then use the calculated field as your parameter field.
If you're feeding the parameter from another application, you have to worry about extra spaces in your punctuation. If you're asking a user for input, not only do they have to match the names, but they also have to match your punctuation format. From the user's perspective, being prompted for three bits of information is more likely to result in a successful match.
I will not be asking for user input, but instead they will select from the default values which i extracted from the database. My fields are LastName, FirstName and MiddleName. I will combine these 3 into 1 parameter, so the values in the combo box will look like this "LastName, Firstname, MiddleName"..
Ex. "Davis, Michael, Milby".
Thanks for taking the time to anwer my question. :-)