pictures list need some help

ive got this code here

image_count = 1;
local tblSelected = ComboBox.GetSelected("biletebi2");

if ( not tblSelected ) then
Image.Load("Image1", "AutoPlay\\Images\\carieli_1.JPG");
else
image_count = image_count + 1;

--count

if image_count < Table.Count(image)+1 then
Image.Load("Image1", image[image_count]);



else

image_count=1
Image.Load("Image1", image[image_count]);
Dialog.Message("Info", "there is no more pictures to show..", MB_OK, MB_ICONEXCLAMATION, MB_DEFBUTTON1);

end

end

and it's doing it's job.. but I need reverse it
when I want to bring previous pictures but if there is no any previous picture then show dialog message or something ((( please help...