Question on VBA Script

Function Custom()

   'start from cell A100000 and get the last cell that is above a blank cell
   ' basically an attempt to find out the last cell (not the best way i would say)
   FindLastRow = Range("A100000").End(xlUp).Row
   
   'select the first sheet (first sheet is subjective and again not best way)
   Sheets(1).Select
   
   'on the selected sheet, select cell A1
   Range("A1").Select
   
   'select the curretnly used cells starting from A1
   Selection.CurrentRegion.Select
   
   'sort of column A
   ActiveWorkbook.Worksheets("Sheet1").Sort.SortFields.Add Key:=Range("A1:A" & FindLastRow), _
   SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
   With ActiveWorkbook.Worksheets("Sheet1").Sort
      .SetRange Range("A1:A" & FindLastRow)
      .Header = xlGuess
      .MatchCase = False
      .Orientation = xlTopToBottom
      .SortMethod = xlPinYin
      .Apply
   End With
     
   'select the 2nd sheet (2nd sheet is subjective and again not best way)
   Sheets(2).Select
   
   ' as before from here
   FindLastRowSort = Range("A100000").End(xlUp).Row
   Range("A1").Select
   Selection.CurrentRegion.Select
   ActiveWorkbook.Worksheets("Sheet2").Sort.SortFields.Clear
   ActiveWorkbook.Worksheets("Sheet2").Sort.SortFields.Add Key:=Range("B1:B" & FindLastRowSort), _
   SortOn:=xlSortOnValues, Order:=xlAscending, DataOption:=xlSortNormal
   With ActiveWorkbook.Worksheets("Sheet2").Sort
      .SetRange Range("A1:B" & FindLastRowSort)
      .Header = xlGuess
      .MatchCase = False
      .Orientation = xlTopToBottom
      .SortMethod = xlPinYin
      .Apply
   End With

End Function