Perform calculation on cells if they have data - excel

Question

I am a bit new to the macro's in excel and I am trying to find a way to adjust one of the macros I currently have in an excel file. I have a calculation that takes the columns D and E then subtracts D from E and adds it to the value of column B. here is the current code and also the sheet being used.
Sub InvAdj()
'
' InvAdj Macro
'
' Keyboard Shortcut: Ctrl+Shift+I
'
Columns("C:C").Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
Range("C1").Select
ActiveCell.FormulaR1C1 = "Quality"
Range("C2").Select
ActiveCell.FormulaR1C1 = "=RC[-1]-RC[2]+RC[3]"
Range("C2").Select
Selection.AutoFill Destination:=Range("C2:C33")
Range("C2:C33").Select
Columns("C:C").Select
Selection.Copy
Columns("B:B").Select
Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=True, Transpose:=False
Columns("C:C").Select
Application.CutCopyMode = False
Selection.Delete Shift:=xlToLeft
Range("D2:E33").Select
Selection.ClearContents
Range("F1").Select
End Sub

Answer 1

Not sure if this is what you are trying?
Sub InvAdj()
Dim ws As Worksheet
'~~> Change this to the relevant sheet
Set ws = ThisWorkbook.Sheets("Sheet1")
With ws
.Range("B1").Value = "Quality"
For i = 2 To 33
'~~> Check if all cells have data
If Len(Trim(.Range("B" & i).Value)) <> 0 And _
en(Trim(.Range("D" & i).Value)) <> 0 And _
en(Trim(.Range("E" & i).Value)) <> 0 Then
'B = B + (E - D)
.Range("B" & i).Value = .Range("B" & i).Value + _
(.Range("E" & i).Value - .Range("D" & i).Value)
End If
Next i
End With
End Sub