set aList to make2DBlankArray(3, 4) of me
set aList to setItemByXY(2, 3, aList, "@") of me
set aRes to getItemByXY(2, 3, aList, "") of me

return aList
–> {{"", "", ""}, {"", "", ""}, {"", "@", ""}, {"", "", ""}}

on getItemByXY(aX, aY, aList, aBlankItem)
　　try
　　　　set aContents to contents of (item aX of item aY of aList)
　　on error
　　　　set aContents to aBlankItem
　　end try
　　return aContents
end getItemByXY

on setItemByXY(aX, aY, aList, aContents)
　　set (item aX of item aY of aList) to aContents
　　return aList
end setItemByXY

–空白の2D Array を出力する
on make2DBlankArray(curLen, curMax)
　　set outArray to {}
　　repeat curMax times
　　　　set aList to {}
　　　　repeat curLen times
　　　　　　set the end of aList to ""
　　　　end repeat
　　　　set the end of outArray to aList
　　end repeat
　　return outArray
end make2DBlankArray