'**************************************
    ' Name: UK Post Code Checker / Validator
    '     
    ' Description:Use in Form Validation to 
    '     check that a supplied UK Post Code is in
    '     the correct format, i.e. has letters and
    '     numbers in the correct places.
    Will format the post code correctly by return.
    Does Not check that the Post Code exists.
    ' By: David Morgan
    '
    ' Inputs:Alleged Post Code string to be 
    '     checked
    '
    ' Returns:True if the string conforms to
    '     the UK post code syntax.
    False if the String does Not conform To the UK post code syntax.
    '
    ' Assumes:Three Functions.
    1) Checks that a character is A - Z
    2) Checks that a character is 1 - 9
    3) Calls the above Functions as it works it's way through the supplied post code string.
    '
    ' Side Effects:The 'passed in' string wi
    '     ll be converted to upper case and have a
    '     space inserted in the correct place.
    '
    'This code is copyrighted and has    ' limited warranties.Please see http://w
    '     ww.Planet-Source-Code.com/vb/scripts/Sho
    '     wCode.asp?txtCodeId=7843&lngWId;=4    'for details.    '**************************************
    
    function IsValidPostCode(ByRef vPostCode)
    	Dim stChar
    	if Len(vPostCode) < 5 Then Exit function
    	vPostCode = Replace(vPostCode, " ", "")
    	Select Case Len(vPostCode)
    		Case 5 ' A1 1AA
    			if Not ValidateAlpha(Left(vPostCode, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 2, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 3, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 4, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 5, 1)) Then Exit function
    			vPostCode = UCase(Left(vPostCode, 2) & " " & Mid(vPostCode, 3))
    			IsValidPostCode = True
    			Exit function
    		Case 6 ' A11 1AA
    			if Not ValidateAlpha(Left(vPostCode, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 2, 1)) And Not ValidateAlpha(Mid(vPostCode, 2, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 3, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 4, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 5, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 6, 1)) Then Exit function
    			vPostCode = UCase(Left(vPostCode, 3) & " " & Mid(vPostCode, 4))
    			IsValidPostCode = True
    			Exit function
    		Case 7 ' AA11 1AA
    			if Not ValidateAlpha(Left(vPostCode, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 2, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 3, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 4, 1)) Then Exit function
    			if Not ValidateNumber(Mid(vPostCode, 5, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 6, 1)) Then Exit function
    			if Not ValidateAlpha(Mid(vPostCode, 7, 1)) Then Exit function
    			vPostCode = UCase(Left(vPostCode, 4) & " " & Mid(vPostCode, 5))
    			IsValidPostCode = True
    			Exit function
    		Case Else
    			Exit function
    	End Select
    	vPostCode = UCase(vPostCode)
    End function
    function ValidateAlpha(vChar)
    	vChar = Asc(LCase(vChar))
    	if Not (vChar > 96 And vChar < 123) Then
    		Exit function
    	Else
    		ValidateAlpha = True
    	End if
    End function
    function ValidateNumber(vNumber)
    	if Not IsNumeric(vNumber) Then
    		Exit function
    	Else
    		vNumber = CLng(vNumber)
    		if vNumber < 1 Or vNumber > 9 Then
    			Exit function
    		Else
    			ValidateNumber = True
    		End if
    	End if		
    End function