store in database if value is other dept from textbox.

Question

Records are being saved from the combobox. But if the value of the combobox is in other department, then how can the value of the textbox be saved in the same column instead of the combobox?

 

exa.

 

if i have combo1 in combo 1 their is 34 department and 35th department is "other department"  

if i select other department in combo1 then textbox should be enable and whatever i enter in textbox name of department it should be save in same column in table instead of combo1