Mandatory field required message when user skips mandatory fields

Hi,

I have set of column A to V in which E, G, H, I, K, M,P, Q, R, T, U, V are mandatory. User might need to enter values in the other columns at a later stage.

Can anyone help with a macro to check whether the mandatory fields are entered by the user once they save the data or if they abruptly close the excel without saving they must be asked whether to save and then show them a message on the missing mandatory fields.