Variable number of rows in a macro

Hi all!

I'm trying to write a macro with a variable number or rows depending on the total number of rows the workbook has.

I tried like this:

Sub provaanova()

     Application.Run "ATPVBAEN.XLAM!Regress", ActiveSheet.Range(("$J$2:$J$") & Range("J" & Rows.Count).End(xlUp).Row) _
        , ActiveSheet.Range(("$J$2:$J$") & Range("J" & Rows.Count).End(xlUp).Row), False, False, 99, "ANOVA", False, _
        False, False, False, , False
    Cells.Select
    Cells.EntireColumn.AutoFit
    Range("A1").Select
End Sub

but it gives me an error. The only way i was able to do it without error was:

Sub Provaregress()

     Application.Run "ATPVBAEN.XLAM!Regress", ActiveSheet.Range("$J$2:$J$53968") _
        , ActiveSheet.Range("$K$2:$M$53968"), False, False, 99, "ANOVA", False, _
        False, False, False, , False
    Cells.Select
    Cells.EntireColumn.AutoFit
    Range("A1").Select
End Sub

but as u can see it has a fixed number of rows.

I'm not a 'pro' programmer in excel, i'm just starting learning, so any help is really appreciated!

thanks