How to fill datagridview based on selection of another combobox

I have ComboBox Contain faculties ,then after select any faculty I need to fill DataGridView By Details of this faculty , the details are departments and number of every ,all department must loaded into combobox inner datagridvew ,I mean when I select faculty the combobox in datagridvew must contain departments of this faculty and number of students in this faculty in the same row ,and when I select another department from combbox the number of student must be change

thank you ^^ 

<pre>I have ComboBox Contain faculties ,then after select any faculty I need to fill DataGridView By Details of this faculty , the details are departments and number of every ,all department must loaded into combobox inner datagridvew ,I mean when I select faculty the combobox in datagridvew must contain departments of this faculty and number of students in this faculty in the same row ,and when I select another department from combbox the number of student must be change

thank you ^^