Login Problems

I have created a ms access front end to SQL database.

I have used the below vb to create the user login function, but it is
not working, i believe that this is because the 'password' field in the sql database
is set to the password format, is there some extra code i need to enter to get the
login script to work.

** also i am using a different systems user table (so i don';t have to keep it up to date!
but users can change their password, this seeem to then be stored in several fields Password, Password#2, password#3 etc.
so when i need to authenticate users, i will have to check all these password fields to make sure....

any help would be greatly appreciated...

Private Sub cmdLogin_Click()
If IsNull(Me.username) Or Me.username = "" Then
MsgBox "You must enter a User Name.", vbOKOnly, "Required Data"
Me.username.SetFocus
Exit Sub
End If
If IsNull(Me.pword) Or Me.pword = "" Then
MsgBox "You must enter a Password.", vbOKOnly, "Required Data"
Me.pword.SetFocus
Exit Sub
End If
If Me.pword.Value = DLookup("[Password]", "tblUser", "[PayrollNo]=" & Me.username.Value) Then
MyPayrollNo = Me.username.Value
DoCmd.Close acForm, "LogOn", acSaveNo
DoCmd.OpenForm "Welcome"
Else
MsgBox "Password Invalid. Please Try Again", vbOKOnly, "Invalid Entry!"
Me.pword.SetFocus
End If
intLogonAttempts = intLogonAttempts + 1
If intLogonAttempts > 3 Then
MsgBox "You do not have access to this database.Please contact admin.", vbCritical, "Restricted Access!"
Application.Quit
End If
End Sub

thanks