Userform Entering Data to a spreadsheet

[nir020]

I have created a userform that uses a number of comboxes to allow users to
input data into a spreadsheet.

In this way I can restrict what data is entered.

I want to write a method which when users clicks the submit button checks if
any of the combo boxes are empty and if so informs the user and does not
input the data to the spreadsheet.

I also want to know if there is a quick way of resetting all the combox back
to blank after the data has been submitted, when the userform is initalised
they are set this way.

Thanks