change textbox depend on selection change in ComboBox column of datagridview

[linkl]

I have a DGV I am working on, and I have many columns.

For example I have Columns colcase(Combobox), colreportTime(Time)

the combox shows 4 cases {A,B,C,D}

what I need to do is if the user select "C"

the the colreporttime will show the time of this change unless the old value is C



I am new to DGV so any help would be great.