Inserting and formating date with userform

Hello,

I am trying to Insert a date with a Textbox in a Userform.

It should have this format: Friday, 18.08.2017.

This entered Date is used in a Formula which I didn't define via vba.

The Formula is:

=WENN(ISTLEER(E251);"";DATUM(JAHR(E251);MONAT(E251)+D251;TAG(E251)))

How do I insert the date, that it can be used with my formula?

My code so far:

Private Sub CommandButton1_Click()


zeile = Cells(Rows.Count, 1).End(xlUp).Row + 1

    Cells(zeile, 1) = ComboBox1.Text
    Cells(zeile, 2) = TextBox1.Text
    Cells(zeile, 3) = ComboBox2.Text
    Cells(zeile, 4) = ComboBox3.Text
    Cells(zeile, 5) = Format(TextBox2.Text, "dddd,d mmmm yyyy")
    Cells(zeile, 8) = TextBox3.Text

Cheers

Scencea