Example code:
#include <Excel.au3>
Global $aData1[][] = [[11, 12], [21, 22], [31, 32]]
Global $aData2[][] = [["A", "B"], ["C", "D"]]
Global $iCurrentRow = 1
Global $oExcel = _Excel_Open()
Global $oWBIn[2]
$oWBIn[0] = _Excel_BookNew($oExcel)
$oWBIn[1] = _Excel_BookNew($oExcel)
Global $oWBOut = _Excel_BookNew($oExcel)
_Excel_RangeWrite($oWBIn[0], 1, $aData1)
_Excel_RangeWrite($oWBIn[1], 1, $aData2)
For $i = 0 To UBound($oWBIn) - 1
_Excel_RangeCopyPaste($oWBIn[$i].Worksheets(1), $oWBIn[$i].Worksheets(1).Usedrange, $oWBOut.Worksheets(1).Range("A" & $iCurrentRow))
$iCurrentRow = $iCurrentRow + $oWBIn[$i].Worksheets(1).Usedrange.Rows.Count
Next