[Old Pedant]

NOTHING is the VBScript equivalent of null in JS.

You can try it. Dunno if it will work.

var connString = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source='database.mdb'";
var adoconn = new ActiveXobject("ADODB.Connection");
adoconn.Open(connString);
var adoRS = new ActiveXobject("ADODB.Recordset");

var strSQL = "Select SUM(database_column_name) As Total FROM xMarvin";
adoRS = adoconn.Execute(strSQL);
textbox1.value = adoRS.Fields(0);
adoRS.Close();
adoRS = null;

... so your update ...

adoconn.Close();
adoconn = null;

var adoconn = new ActiveXobject("ADODB.Connection");
adoconn.Open(connString);
adoRS = adoconn.Execute(strSQL);
textbox1.value = adoRS.Fields(0);
adoRS.Close();
adoconn.Close();

// if needed:
adoRS = null;
adoconn = null;