Ive made a Security Screensaver whit the options to show random pictures. and it show the start time, time went and then im trying to get it to show time left by minus lasttime whit currenttime

It just doesnt work,
if anyone could help me i would very much appreciate it this is how the code looks:

procedure TForm7.TimerSecTimer(Sender: TObject);
var item : tlistitem; N : integer; randomnr : integer; x : integer; startime : tdatetime; timeleft : tdatetime; lasttime : tdatetime; currenttime : tdatetime;
begin
if i = Listview1.Items.Count -1 then
begin
if checkbox1.Checked = true then
begin
i := 0;
item := listview1.Items[i];
form2.image1.Picture.LoadFromFile(item.Caption);
end
else
begin
timersec.Enabled := false;
end;
end
else
begin
if checkbox2.Checked = true then
begin

if checkbox5.Checked = false then timersec.Enabled := false;

form2.Label9.Caption := 'Start time:' + timetostr(now); {here i show the start time}
startime := now; {saves the starttime}

randomnr := random(listview1.Items.Count -1);

form2.ProgressBar1.Max := listview1.Items.Count;

for n:=1 to ListView1.Items.Count do
begin
application.ProcessMessages;

if form2.checkbox1.checked = true then break;


form2.ProgressBar1.Position := form2.ProgressBar1.Position + 1;

form2.LblList1.Caption := 'Lisview1 : ' + inttostr(form2.ProgressBar1.Position) + ' out of ' + inttostr(form2.ProgressBar1.Max);

SetWindowPos(form3.Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);

if checkbox3.Checked = true then
begin


x := 0;
form2.ProgressBar2.Max := listview2.Items.Count;
While x<listview2.Items.Count do
begin

application.ProcessMessages;
if form2.checkbox1.checked = true then break;

if inttostr(randomnr) = listview2.Items[x].Caption then
begin


form2.Label2.Caption := 'Randum number found... Generating new one!';
randomnr := random(listview1.Items.Count);
x := 0;
form2.ProgressBar2.Position := 0;

SetWindowPos(form3.Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);
end
else
begin

form2.ProgressBar2.Position := form2.ProgressBar2.Position + 1;

form2.LblList2.Caption := 'Lisview2 : ' + inttostr(form2.ProgressBar2.Position) + ' out of ' + inttostr(form2.ProgressBar2.Max);

form2.Label2.Caption := 'Processing...';
x := x +1;

form2.Label10.Caption := 'Time went: ' + timetostr(now - startime); { here i show how much time has gone.}
currenttime := now - startime; {here the "Currenttime" gets updated}

timeleft := lasttime - currenttime; {here i calculate timeleft whit lasttime - currenttime. But it count upwards instead of down}
form2.label12.caption := 'Time left:' + timetostr(timeleft); {here i show timeleft}

SetWindowPos(form3.Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);
end;
end;
end;
form2.ProgressBar2.Position := 0;
end;


if form2.CheckBox1.Checked = false then
begin

item := listview1.Items[randomnr];
form2.image1.Picture.LoadFromFile(item.Caption);

SetWindowPos(form3.Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);

form2.label8.Caption := 'Size of image: ' + inttostr(getfilesize(item.Caption) div 1024) + ' KB';
form2.Label7.Caption := item.Caption;

SetWindowPos(form3.Handle, HWND_TOPMOST, 0,0,0,0, SWP_NOACTIVATE or SWP_NOMOVE or SWP_NOSIZE);

item := listview2.Items.Add;
item.Caption := inttostr(randomnr);

form2.ProgressBar1.Position := 0;
form2.ProgressBar2.Position := 0;

form2.Label11.Caption := 'Time for last picture: ' + timetostr(now - startime); {Here i show how long it was to calculate the last picture}
lasttime := now - startime; {here i save the time for the last image.}

if listview1.Items.Count = listview2.Items.Count then listview2.Clear;
if (checkbox5.Checked = false) and (lockdown = true) then timersec.Enabled := true;
end;



end
else
begin
i := i + 1;
item := listview1.Items[i];
form2.image1.Picture.LoadFromFile(item.Caption);

form2.label8.Caption := 'Size of image: ' + inttostr(getfilesize(item.Caption) div 1024) + ' KB';
form2.Label7.Caption := item.Caption;
end;
end;
End;

Best regards,
Darkyere