Type Mismatch string

Hello Everyone, I want in my number fields to have commas be added to it after the user clicks Tab....
After the page is submitted it goes to a page called 2.asp which is a validation page, and here the commas are removed before the number is entered into the database, however, when I return to the original page to make the changes suggested on 2.asp, I sitll want the numbers to retain the commas, no decimaal points, and no dollar sign in front of the number in the textbox... because there is a dollar sign outside the text box:
                    ______________
Like this:   $ |_________1,000|    
Also I cannot have the $ inside the box because the computer will think it's a number and add a comma after it like this:   $,345    :(

The datatype in the database for this field is money  
The problem is that my code is giving me the following ERROR which comes from the first page:

Microsoft VBScript runtime error ‘800a000d’
Type Mismatch: ‘FormatNumber’

Error comes from Line 636 which is this line:    <input style="font-family: Verdana; font-size: 8pt" type="text" value="<%=FormatNumber(strSales,0)%>" name="txtSales" size="14" maxlength="11" align="right" onblur="this.value = Comma(this.value)"; />


And I also get this  ERROR: from line 305 from the second page: "2.asp"
This line is:          <% if (strSales="" or strSales = 0) Then %><span class="reqfld">Required Field</span><% Else %>$<%=strSales%><% End If %></td>

Microsoft VBScript runtime (0x800A000D)
Type mismatch: '[string: ""]'

This comes from line


‘**********************************Code on the first page:  *****************************************************

<form name="save50P1" method="post" action="2.asp" onsubmit="return ValidateSubmit();" onkeypress="return event.keyCode!=13">

<table cellpadding="0" cellspacing="3" border="0" width="558">
<tr>
<td valign="top" align="left" width="15"></td>
<td valign="top" align="left">Contact<font color = "red"> * </font>:</td>
<td valign="top" align="left"><input style="font-family: Verdana; font-size: 8pt" type="text" value="<%=strContact%>" size="50"   name="txtContact" /></td>            
</tr>
<tr>
<td valign="top" align="left" width="440">Annual sales:</td>
<td valign="top" align="left">$&nbsp;
<span id="rInputs">
<input style="font-family: Verdana; font-size: 8pt" type="text" value="<%=FormatNumber(strSales,0)%>" name="txtSales" size="14" maxlength="11" align="right" onblur="this.value = Comma(this.value)"; />
 </span> </td></tr></table>
</td>            
</tr>      
</table>

<script>
function Comma(number) {
number = '' + number;
      if (number.length > 3) {
            var mod = number.length % 3;
            var output = (mod > 0 ? (number.substring(0,mod)) : '');
            for (i=0 ; i < Math.floor(number.length / 3); i++) {
            if ((mod == 0) && (i == 0))
            output += number.substring(mod+ 3 * i, mod + 3 * i + 3);
      else
            output+= ',' + number.substring(mod + 3 * i, mod + 3 * i + 3);
      }
      return (output);
  }
else return number;
}
</script>

‘*******************************8Code on the second page (2.asp): the VALIDATION PAGE***********************

<script>
function CheckWord(CheckValue)
  CheckValue = replace(CheckValue, "&" , "&amp;")
  CheckValue = replace(CheckValue, "<", "&lt;")
  CheckValue = replace(CheckValue, ">", "&gt;")
  CheckValue = replace(CheckValue, "'", "''")
  CheckValue = replace(CheckValue, "%20", " ")
  CheckValue = replace(CheckValue, ";"," " )
  CheckValue = trim(CheckValue)
  CheckValue=replace(CheckValue,",","")
  CheckWord=CheckValue
end function

function fnCheckForNumber(strNum)
      If NOT isNumeric(replace(fnStripCommas(strNum),".","")) Then
            strNum="NULL"
            'Angie H. -- Change NULL to blank
            strNum=""
            totalblank=totalblank+1
      End If
      if (strNum="") Then
            strNum="NULL"
            'Angie H. -- Change NULL to blank
            strNum=""
      End If
      fnCheckForNumber=fnStripCommas(strNum)
End Function

function fnStripCommas(sInput)
  if isNull(sInput) or isEmpty(sInput) or sInput="$" then
'    fnStripCommas="NULL"
      'Angie H. -- Change NULL to blank
      fnStripCommas=""
  else
    fnStripCommas=replace( replace(sInput,",",""), "$", "" )
  end if
end function
</script>


<%
if not objRS.eof then
strContact=fnEmptyIfNull(objRS("txtContact"))
strSales=fnEmptyIfNull(objRS("txtSales"))
End If      


strSQL = "UPDATE form50 set "
strSQL = strSQL & " txtContact='" & CheckWord(fnNullIfEmpty(request.form("txtContact"))) & "', "
            if (Len(request.form("txtSales"))<1) Then
                  tempsales="NULL"
            Else
                  tempsales=fnCheckForNumber(CheckWord(request.form("txtSales")))
            End If
strSQL = strSQL & " txtSales=" & tempsales & " "            
strSQL = strSQL & " WHERE UserID=" & Session("UserID")
objConn.Execute(strSQL)

Any ideas what is wrong, is it the fact that I used FormatNumber() instead of FormatCurrency
If that is the case, how do I use FormatCurrency without the $ to show up because that would give me other problems such as the comma thinking it's a number and adding itself after it like this

$,323,000


BTW: I am coding in ASP, using SQL Server 2000 as the database