Maybe something like this? 
 
#include <Excel.au3>
; Pass the following parameters:
;  * Object of the Workbook
;  * Number or Name of the Worksheet
;  * Name or Index number of the table
;  * Name or Index number of the Column
Func FindLastRowInExcelTable($oWorkbook, $vWorksheet, $sTable, $iColumn)
	Local $xlByRows = 1 ; Searches across a row, then moves to the next row.
	Local $xlPrevious = 2 ; Search for previous matching value in range.
	Local $iLastRow, $oWorksheet, $oTable
	$oWorksheet = $oWorkbook.Sheets($vWorksheet)
	$oTable = $oWorksheet.ListObjects($sTable)
	With $oTable.ListColumns($iColumn).Range
		$iLastRow = .Find("*", .Cells(1), $xlFormulas, $xlPart, $xlByRows, $xlPrevious, False).Row
	EndWith
EndFunc   ;==>FindLastRowInExcelTable