Custom search based on diagnosis

[FTDave]

How difficult would it be to do this?
Say you setup a custom user field with a drop down menu.

The profile ask you to select a certain diagnosis.
diagnosis-A
diagnosis-B
diagnosis-C

Then say a user wants to list everyone with diagnosis-C.

How could it be done?
I'm no expert with php or mysql but can do some.

What ideas do you have?

[Reeve of shinra]

Depends on what your specifically looking to do with it afterward, but if make the field searchable from the member list, you could do an advanced search and pull the users that way. A query pulling just those users into a new page shouldnt be too hard either.