I'd like to preface this answer by saying I don't recommend using VBA for this. It's much better to keep the value being typed separate from the calculations. Use three columns.
That being said, if you're set on the requested approach, you can try this:
Open the Visual Basic Editor using Alt+F11.
In the Project explorer, double-click the Sheet on which you want the calculation to happen. If you don't see the Project explore as shown in this image, go to View>Project Explorer, or alternatively press Ctrl+R.
Paste the following code into the code window.
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim hours As Integer
' only do something if C2 was changed
If Target.AddressLocal = "$C$2" And Target <> "" Then
' get the value that was typed into cell C2
hours = Target
' disable the events so that updating C2 to the required date will not execute this macro again
Application.EnableEvents = False
' update C2 to be that portion of a day after the date/time in cell B2
Target = Target.Offset(0, -1) + (hours / 24)
' enable the events
Application.EnableEvents = True
End If
End SubThis code will execute every time a change is made on Sheet1. If the cell that was changed is cell C2, it will execute the steps shown (i.e. it will update C2 to be x hours after B2, if x is typed into C2).
Assumptions:
1. "In" is in cell B2
2. "Out" is in cell C2
As you can see, if I type a value into cell C2, it is updated to that many hours after the date/time in cell B2:
If you want to apply this to many rows, it can be changed somewhat easily, so let me know if that's the case.