PHP programming

i have a simple query :

$query1 = "SELECT count( ID_Bimbingan ) AS jumlah FROM `tblbimbingan` WHERE NIM = (SELECT `NIM` FROM `tblmhs` WHERE `".$_POST['cmbKriteria']."` LIKE '%".$_POST['txtCari']."%') && Approve1 =TRUE && Approve2 =TRUE";

I've add this query in my combo box like this :

<option value="Nama_Mhs">Nama Mahasiswa</option>

but still can't solve and still error and appear :

Unknown column 'Nama_Mhs' in 'where clause'

I wish i can solve this problem, need the help thank you