How to apply code to all the following rows - excel

Question

I have this code but it only work for my first row.
It is suppose to look if the checkbox on B, C or D is checked, and if so, a date + username will automaticaly fill in F and G.
here is a picture of my table:
This is what my code looks like:
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
If Range("B2") Or Range("C2") Or Range("D2") = True Then
Range("G2").Value = Environ("Username")
Range("F2").Value = Date
Else
Range("F2:G2").ClearContents
End If
End Sub

Answer 1

Enter this code in a regular module, select all your checkboxes and right-click >> assign macro then choose ReviewRows.
This will run the check whenever a checkbox is clicked - a bit of overhead since all rows will be checked, but should not be a big deal.
Sub ReviewRows()
Dim n As Long
For n = 1 To 100 'for example
With Sheet1.Rows(n)
If Application.CountIf(.Cells(2).Resize(1, 3), "TRUE") > 0 Then
If Len(.Cells(6).Value) = 0 Then 'only enter if currently empty?
.Cells(6) = Date
.Cells(7) = Environ("Username")
End If
Else
.Cells(6).Resize(1, 2).ClearContents
End If
End With
Next n
End Sub
If you want to be more precise then Application.Caller will give you the name of the checkbox which was clicked, and you can use that to find the appropriate row to check via the linkedCell.
Sub ReviewRows()
Dim n As Long, shp As CheckBox, c As Range, ws As Worksheet
Set ws = ActiveSheet
On Error Resume Next 'ignore error in case calling object is not a checkbox
Set shp = ActiveSheet.CheckBoxes(Application.Caller) 'get the clicked checkbox
On Error GoTo 0 'stop ignoring errors
If Not shp Is Nothing Then 'got a checkbox ?
If shp.LinkedCell <> "" Then 'does it have a linked cell ?
With ws.Range(shp.LinkedCell).EntireRow
If Application.CountIf(.Cells(2).Resize(1, 3), "TRUE") > 0 Then
If Len(.Cells(6).Value) = 0 Then 'only enter if currently empty?
.Cells(6) = Date
.Cells(7) = Environ("Username")
End If
Else
.Cells(6).Resize(1, 2).ClearContents
End If
End With
End If 'has linked cell
End If 'was a checkbox
End Sub
However this appraoch is sensitive to the exact positioning of your checkbox

Answer 2

You have a long way to go!
Unfortunately, If Range("B2") Or Range("C2") Or Range("D2") = True Then is beyond repair. In fact, your entire concept is.
Start with the concept: Technically speaking, checkboxes aren't on the worksheet. They are on a layer that is superimposed over the worksheet. They don't cause a worksheet event, nor are they responding to worksheet events. The good thing is that they have their own.
If Range("B2") Or Range("C2") Or Range("D2") = True Then conflates Range with Range.Value. One is an object (the cell), the other one of the object's properties. So, to insert sense into your syntax it would have to read, like, If Range("B2").Value = True Or Range("C2").Value = True Or Range("D2").Value = True Then. However this won't work because the trigger is wrong. The Worksheet_Change event won't fire when when a checkbox changes a cell's value, and the SelectionChange event is far too common to let it run indiscriminately in the hope of sometimes being right (like the broken clock that shows the correct time twice a day).
The answer, therefore is to capture the checkbox's click event.
Private Sub CheckBox1_Click()
If CheckBox1.Value = vbTrue Then
MsgBox "Clicked"
End If
End Sub
Whatever you want to do when the checkbox is checked must be done where it now shows a MsgBox. You can also take action when it is being unchecked.