You are making your life unnecessarily difficult. All dates are represented by numbers like 43218.75 where the integer defines the day and the decimals the time. In this example, 0.75 days have lapsed since midnight on day 43218 (April 28, 2018). Therefore 43218.75 stands for 6:00PM on Apr 24, 2018. It follows that 43210.75 would be 8 days earlier and, therefore, 43218.75 - 43210.75 would be the date difference in days. Use the Int() function to extract the date from a Date/Time value.
The CDate() function extracts a date from either a string or a number. Therefore if your range C35 holds a true date (as a number) or a string, like "24/4/2018"
CDate(Range("C35").Value) will return a number which you can compare with another number similarly created. Hence the following code.
Private Sub TestFunction()
MsgBox "Date difference is " & ogv("C35") & " days."
Function ogv(CellAddress As String) As Integer
ogv = Abs(Int(CDate(.Value)) - Int(CDate(.Offset(-1).Value)))
Use the Sub to test call the function. Use the code in the sub in your VBA project.