How to add a select all check boxes option to a UserForm in Excel VBA

So I have this code

Dim LastRow     As Long

Private Sub Remove_Files_Button_Click()


On Error GoTo Error:
Dim i As Long
For i = 1 To LastRow
    If Me.Controls("CheckBox_" & i) Then
        Range("G" & i).Value = Range("A" & i).Value
    End If
    If Me.Controls("CheckBox_" & i) Then
        Range("H" & i).Value = Range("B" & i).Value
    End If
    If Me.Controls("CheckBox_" & i) Then
        Range("I" & i).Value = Range("C" & i).Value
    End If
Next i
    Range("A:F").Select
    Selection.Delete Shift:=xlToLeft
    Range("A:B").Sort Key1:=Range("A1"), Order1:=xlAscending, Header:=xlNo
Error:
    Unload Me
End Sub


Sub UserForm_Initialize()

Dim i           As Long
Dim chkBox      As MSForms.CheckBox

On Error GoTo Error:
LastRow = Worksheets("Sheet1").Cells(Rows.Count, 1).End(xlUp).Row

For i = 1 To LastRow
    Set chkBox = Me.Controls.Add("Forms.CheckBox.1", "CheckBox_" & i)
    chkBox.Height = 30
    chkBox.Caption = Worksheets("Sheet1").Cells(i, 1).Value
    chkBox.Left = ((i - 1) Mod 4) * 100 + 5
    chkBox.Top = 5 + Fix((i - 1) / 4) * 30
Next i
Error:
End Sub

in a VBA form. and when I run it i generate this pop-up enter image description here

What I would like to do and haven't been able to figure out even how to go about it is have a second button that if clicked would automatically select all check boxes. Any help would be appreciated. Thanks