SELECT Mlist.[Date List Produced], Mlist.[COMPANY NAME], Mlist.ADDRESS,

  Mlist.CITY, Mlist.STATE, Mlist.[XZIP CODE], Mlist.COUNTY,

  Mlist.[LAST NAME], Mlist.[FIRST NAME], Mlist.[CONTACT TITLE], Mlist.[CONTACT GENDER],

  Mlist.[CONTACT PROF TITLE], Mlist.BuySell, Mlist.YearOfGrad, Mlist.[LOCATION ADDRESS],

  Mlist.[LOCATION ADDRESS CITY], Mlist.[LOCATION ADDRESS STATE], Mlist.ZIP,

  Zip_codes.Latitude AS Latitude, Zip_codes.Longitude AS Longitude

FROM Mlist INNER JOIN Zip_codes ON Mlist.ZIP = Zip_codes.Zipcode

WHERE (((GeoDistance(CSng([Longitude]),CSng([Latitude]),

  CSng((SELECT Longitude FROM Zip_codes WHERE Zipcode= Forms![Locate]![ZipTxt] )),

  CSng((SELECT Latitude FROM Zip_codes WHERE Zipcode= Forms![Locate]![ZipTxt] )),"mi"))

  <=CInt([Forms]![Locate]![DistanceTxt])));

   Public Function GeoDistance(Long1, Lat1, Long2, Lat2, Units)

' Constant to convert degrees into radians
  Const k As Double = 3.14159265358979 / 180
  
' Flattening of the earth
  Const ff As Double = 1 / 298.257

  Dim C  As Double
  Dim D  As Double
  Dim F  As Double
  Dim G  As Double
  Dim H1 As Double
  Dim H2 As Double
  Dim L  As Double
  Dim O  As Double
  Dim R  As Double
  Dim S  As Double
  Dim W1 As Double
  Dim W2 As Double
  Dim W3 As Double
  Dim W4 As Double
  Dim SG As Double
  Dim CG As Double
  Dim SF As Double
  Dim CF As Double
  Dim SL As Double
  Dim CL As Double
  Dim U  As String
  Dim UF As Double
  

     U = LCase(Trim(Units))
    UF = 1
  If U = "mi" Then UF = 1.609344
  If U = "nmi" Then UF = 1.852
  
counter = counter + 1

  
' Compute auxiliary angles
  F = (CSng(Lat1) + CSng(Lat2)) / 2
  G = (CSng(Lat1) - CSng(Lat2)) / 2
  L = (CSng(Long1) - CSng(Long2)) / 2
  
'covers when comparing the same location
If G = 0 And L = 0 Then
    GeoDistance = 0
    Exit Function
End If
  
' Compute sines and cosines of auxiliary angles
  SG = Sin(G * k)
  CG = Cos(G * k)
  SF = Sin(F * k)
  CF = Cos(F * k)
  SL = Sin(L * k)
  CL = Cos(L * k)

W1 = SG * CL: W1 = W1 * W1
W2 = CF * SL: W2 = W2 * W2
  S = W1 + W2

W3 = CG * CL: W3 = W3 * W3
W4 = SF * SL: W4 = W4 * W4
  C = W3 + W4

  O = Atn(Sqr(S / C))
  R = Sqr(S * C) / O
  D = 2 * O * 6378.14

H1 = (3 * R - 1) / (2 * C)
H2 = (3 * R + 1) / (2 * S)

' Compute the angle between the points on a
' synthetic sphere connecting the two points.
  W1 = SF * CG: W1 = W1 * W1 * H1 * ff + 1
  W2 = CF * SG: W2 = W2 * W2 * H2 * ff

' Return the distance between the given locations in
' the units indicated by the units factor UF
  GeoDistance = D * (W1 - W2) / UF

  End Function