Display combobox selected item in DataGridview

Sir, I am doing a ADO.NET Project.

my form has 1)comboboxes;

a)cmbclass(to display className)

b) cmbDivision(to divisionName)

c) cmbExam(to examName)

d) cmbSubject(to display subjectName)

2) Datagridview. it has five columns; name, temark,ceMark,peMark and Total

And my tasks are:-

1)when i select className and divisionName, i want to display that in datagridview.

2) when i enter mark, Total column to be increment the mark of each columns.

please help me in this.