I recently had a similar issue... the only way I have been able to get it to work when trying to query like you are is to first store that recordset as a variable because you need the percentage sign for the like variable - but since it is part of the variable in the method you are using, it will result in an error.
So the way to stop the error is to rewrite the query like this:
$valuetocheck = $colname_Recordset1;
$query_Recordset1 = sprintf("SELECT * FROM tblcategory WHERE `Description` LIKE '%$valuetocheck%' ";
$Recordset1 = mysql_query($query_Recordset1, $connection) or die(mysql_error());
$row_Recordset1 = mysql_fetch_assoc($Recordset1);
$totalRows_Recordset1 = mysql_num_rows($Recordset1);