Calculation that searches all values in an attribute

Hi All

I've gone a bit wild and tried to create a calculation that will check, as part of a condition, whether a username already exists in the database (user.name field in the user table)

This should hopefully redirect the request to a "create this user manually area" of the process. I'm struggling to find out how to search through all of the values stored in the user.name field. This is what I have so far:

import System

static def GetAttributeValue(Request):

  SuggestedUN = Request._NewUserSurname +'.'+ Request._NewUserFirstName

  if Request.RaiseUser.Name == SuggestedUN:

  value = 'Not Available'

The syntax checks ok but there is an object reference error in line

I then went the whole hog and failed again

import System

static def GetAttributeValue(Request):

  value = Request.RaiseUser.Title

  SuggestedUN = Request._NewUserSurname +'.'+ Request._NewUserFirstName

  if Request.RaiseUser.Name != null and Request.RaiseUser.Name == SuggestedUN:

  value = 'Available'

  else:

  value = 'Not Available'

  return value.ToString()

I'm pretty sure that the calculation is not going to do what i need it to do anyway as it's only matching against the name for that request rather than the whole table of user.names

Help appreciated as always

Jason