VBA to display error message if cells (A,B,C) are filled out, but cells (D,E,F) are not?

[NiicckkM]

I am creating a file that requires user-input. If the user begins to fill out the form, I want excel to display an error if they do not finish.

So if I need user input in cells A1, B1, C1, and D1, but the user only fills out A1,B1, and C1, I want excel to display a message saying "All Cells Must be filled. Please fill out cell D1".

This is what I've got so far

If IsEmpty(Range("A1").Value) = False And IsEmpty(Range("B1").Value) = False  And IsEmpty(Range("C1").Value) = False And IsEmpty(Range("D1").Value) = True  Then

MsgBox "All Cells Must be filled. Please fill out cell D1"
End if

End sub

The problem with this is that it will only display the message box if the sub is ran. I would like excel to automatically display this text. Also, is there a more efficient way to write that without so many And-Statements?

Thanks

 

[My Aswer Is This]

I would think you need to create a UserForm. Any time you have a sheet event change the UserForm Pop's up. Put 4 text boxes on the UserForm and then when you click the OK button on the UserForm if you have not filled in all four text boxes you would get a popup alert.
With your wanting to have this automated without a UserForm how would the script know when you started filling in a form and when you had finished.