how to break a code into below line in vba

Range("G2")="=sumifs(B2:B10,A2:A10," & _

"F2)"

Range("M3") = "=G3&"",""&L3": Range("M3:M" & LastRow).FillDown

Sub CopyDown()
Dim Lastrow As String, FirstRow As String, strtCell As Range
'
' CopyDown Macro
' Copies the current cell to any empty cells below it.   
'
' Keyboard Shortcut: Ctrl+Shift+D
'
    Set strtCell = ActiveCell
    FirstRow = strtCell.Address
' Lastrow is address of the *list* of empty cells
    Lastrow = Range(Selection, Selection.End(xlDown).Offset(-1, 0)).Address
'   MsgBox Lastrow
    Range(Lastrow).Formula = strtCell.Formula

    Range(Lastrow).End(xlDown).Select
 End Sub

Range("$M$3").Formula = Range("G3") & (",") & Range("L3")

Dim Lastrow As Long

Application.ScreenUpdating = False

Lastrow = Range("L" & Rows.Count).End(xlUp).Row
Range("M4").FormulaR1C1 = Range("G4") & (",") & Range("L4")
Range("M4").AutoFill Destination:=Range("M4:M" & Lastrow)
ActiveSheet.AutoFilterMode = False
Application.ScreenUpdating = True