VBA Code for Conditional Loop - vba

Question

I am trying to create a conditional loop macro in Excel. Column B contains a last name, Column C contains a first name, and Column D contains a first and last name. I am trying to get the macro to detect when Column D = Column C + Column B.
If D = C + B, then clear contents of D.
So, the following works for a single row:
Sub ClearContentsD ()
If Range("D1").Value = Range("C1").Value + Space(1) + Range("B1") Then Range("D1").ClearContents
End Sub
It does not work without the added Space(1), and I cannot get it to loop through the whole worksheet:
Sub ClearContentsLoop()
Application.ScreenUpdating = False
Dim i As Long
For i = 1 To Rows.Count
Next i
Do While Cells(i, 4).Value = Cells(i, 3).Value + Space(1) + Cells(i, 2).Value
Cells(i, 4).ClearContents
Loop
Application.ScreenUpdating = True
End Sub
VBA doesn't like my Do While. Any help would be greatly appreciated.
CJ

Answer 1

Some issues:
You must concatenate strings with &. The plus (+) is for addition;
Your For loop is not doing anything: its body is empty;
Your Do While Loop will at most run once, because i is not incremented;
It is a mystery why you would want two loops (For and Do While);
A sheet has many rows of which you only use a fraction, so don't loop through all of them (For) and use UsedRange.
Possible correction:
Sub ClearContentsLoop()
Dim i As Long
Application.ScreenUpdating = False
For i = 1 To ActiveSheet.UsedRange.Rows.Count
If Cells(i, 4).Value = Cells(i, 3).Value & " " & Cells(i, 2).Value Then
Cells(i, 4).ClearContents
End If
Next i
Application.ScreenUpdating = True
End Sub

Answer 2

There is a way to ignore the space in the values you are evaluating. Try this:
Application.ScreenUpdating = False
Dim i As Long
For i = 1 To Rows.Count
If InStr(1, Cells(i, 4).Value, Cells(i, 2).Value, vbTextCompare) > 0 And InStr(1, Cells(i, 4).Value, Cells(i, 3).Value, vbTextCompare) > 0 Then Cells(i, 4).ClearContents
Next i
Application.ScreenUpdating = True
Explanation:
By using the InStr function, you are testing for the presence of one text string inside of another, and if at least one match is found, then the function returns a non-zero value (the position where the match was found). In the above example, you are testing for the presence of the first name and last name at the same time, and if both are found, then the code clears out the contents of the cell.
And, as was pointed out in the comments section, you need to do this inside the loop so that all cells down the length of the worksheet are evaluated and updated as specified.
Be sure to test this on a COPY of your original data so that you don't lose the original values in case you want to roll back your changes! ;)