code for updating rows based on a userform combobox selection

Hi,
First of all I appologise if I didn't post this problem correctly, but I'm new to this forum, as well as to excel programming...
I've created two Excel VBA forms: the first one pops up when the Workbook Opens and gives the possibility to:
(1) enter a new project, and in this case Page1 from a Multipage of the second form is shown
and
(2) update an existing project, wich shows Page2 from the Multipage of the second form.
Page2 of the second form contains a ComboBox that is populated with the projects allready entered. When a project is selected, data is retreived into the comboboxes and textboxes of the second form (on both pages), permitting the user to update fields.
My problem resides in the fact that I can't get the form to update an existing record based on the Combobox selection. It only inserts new records, no matter what I do...I've tried various solutions found on the internet, but this being my first vba project, I'm a little overwhelmed by the situation...

I've attached my workbook, where I've changed the captions of the various objects of the forms.

Thank you in advance for your time and help!