Is it possible in Excel to restrict the user to fill out all the desired
fields before it can be sent via email. Example. A client needs to order a
certain product so he/she must now fill in his/her details. The particular
cell has an asteriks stating that this cell/field is a requirement before the
document can be sent.

What is the process to lock this particular cell so that the document is
unable to be sent unless this cell is filled in.

I hope I have made sense.