I have developed a userform calendar in my spreadsheet, but I need to
know how to restrict the dates that can be selected to Friday's ONLY.

You could simply select the Friday for the week of any day the user clicks
on. Here is the code to do that

For a Calendar Control
===================
Private Sub Calendar1_Click()
With Calendar1
.Value = .Value + 6 - Weekday(.Value)
End With
End Sub


For a MonthView Control
===================
Private Sub MonthView1_DateClick(ByVal DateClicked As Date)
With MonthView1
.Value = .Value + 6 - .DayOfWeek
End With
End Sub


Rick