Set a Value as Number (Number Stored as Text warning comes up)

The ComboBox4 is part of a Userform.

Private Sub ComboBox4_Change()

Sheets("Userform Lists").Activate
Range("C23").Value = ComboBox4
Range("C23").NumberFormat = "0.00"
Calculate

End Sub

When I go to the spreadsheet it tells me that this is now Number Stored as Text. I need it to be a number not text so that other calculations work properly. Any ideas? What have I done wrong?