I've never used forms in Excel, aside from the occasional command button.
But surely if clicking the Submit button causes data from the form to be
written to the worksheet even if mandatory fields are not filled in, it's
because you wrote the button_click code to do it that way?

I mean, if you look at the Submit_Click code, it must say to take the data
and copy it to the worksheet?

Maybe you'd better show us the part of the code from the button_click
procedure that displays the message AND EXITS THE SUB rather than going on to
fill in the data.

--- "sam" wrote:
On my excel form, I have text boxes, radio buttons,
and check boxes. And I have marked some fields as
mandatory; if users clicks submit button without
filling out these mandatory fields, they will see a
popup msg box asking them to input data in these
fields. The popup msg box works great when user
forgets to input a data in some mandatory field,
BUT the data in excel sheet is populated once the
user clicks submit button(without filling up a
mandatory field). Once I click the OK button on
the msg box and input the data in the mandatory
field and click submit, the data is again populated
in the excel sheet in a new row.