syntax error

when i click on my update button and try to update a record whith a duplicate user name
i should get a message at the top of the form that reads " this is a duplicate name please select
a new name" but what i get is the following error:

Error Type:
Microsoft JET Database Engine (0x80040E14)
Syntax error (missing operator) in query expression 'UserName='lemonjello'23'.
/suredatainc/Admin/EditUser.asp, line 87

here is the code:

<%
// *** Redirect if username exists
var MM_flag="MM_update";
if (String(Request(MM_flag)) != "undefined") {
var MM_dupKeyRedirect="EditUser.asp?repeat=true";
var MM_rsKeyConnection=MM_conSureData_STRING;
var MM_dupKeyUsernameValue = String(Request.Form("UserName"));
var MM_dupKeySQL = "SELECT UserName FROM Users WHERE UserName='" + MM_dupKeyUsernameValue + "'" + Request("MM_recordId")
var MM_adodbRecordset = "ADODB.Recordset";
var MM_rsKey = Server.CreateObject(MM_adodbRecordset);
MM_rsKey.ActiveConnection = MM_rsKeyConnection;
MM_rsKey.Source = MM_dupKeySQL;
MM_rsKey.CursorType=0;
MM_rsKey.CursorLocation=2;
MM_rsKey.LockType=3;
MM_rsKey.Open(); <------------------------------this is the line it errors on.
if (!MM_rsKey.EOF || !MM_rsKey.BOF) {
// the username was found - can not add the requested username
var MM_qsChar = "?";
if (MM_dupKeyRedirect.indexOf("?") >= 0) MM_qsChar = "&";
MM_dupKeyRedirect = MM_dupKeyRedirect + MM_qsChar + "requsername=" + MM_dupKeyUsernameValue;
Response.Redirect(MM_dupKeyRedirect);
}
MM_rsKey.Close();
}
%>

send help quick, lemonjello

try this line instead

i tried it and this is the error i get now. not sure why tho.

Error Type:
Microsoft JET Database Engine (0x80040E14)
Invalid SQL statement; expected 'DELETE', 'INSERT', 'PROCEDURE', 'SELECT', or 'UPDATE'.
/suredatainc/Admin/EditUser.asp, line 87

p.s. thanks for the help it is greatly appreciated.