Can you pick out a column that's always filled in?
If yes, then maybe you could do this:
Option Explicit
Sub testme()
Dim LastRow As Long
With Worksheets("sheet1")
LastRow = .Cells(.Rows.Count, "A").End(xlUp).Row
End With
MsgBox LastRow & " is the last row with data in column A"
End Sub
if there are two rows of headers, just subtract 2.
MsgBox LastRow - 2 & " is the total number of rows"
But there are lots of ways to get the number rows.