Sub macro_1()
Dim myrange As Range
Dim lastrow As Integer
Dim my_sh As Worksheet
Dim my_wb As Workbook
                 
 Set my_wb = ThisWorkbook
 Set my_sh = ThisWorkbook.Worksheets("supp_sheet")
     
 lastrow = my_sh.Cells(Rows.Count, 1).End(xlUp).Row
 Set myrange = my_sh.Range("A1:X" & lastrow)
 myrange.Select
End Sub

Sub macro_1()
    Dim lastrow As Long

    With Worksheets("supp_sheet")
        lastrow = .Cells(.Rows.Count, 1).End(xlUp).Row
        .Range("A1:X" & lastrow).Select
    End With
End Sub