This is some psuedocode I came up with. Thanks Flight for showing me how to apply some of the code.
procedure SellFirstSlotRunes;
var
x, y: integer;
begin
MMouse(x coordinate of first slot inventory, y coordinate of first slot inventory, 5, 5)
GetMousePos(x, y);
repeat
clickmouse2(mouse_right);
wait(Randomrange(some number, some higher number));
MoveMouse(x, y+70);
wait(Randomrange(some number, some higher number));
clickmouse2(mouse_left);
wait(Randomrange(some number, some higher number));
MoveMouse(x, y);
wait(Randomrange(some number, some higher number));
until(whenever I want it to end)
end;
This way there would be a human-like action delay (pressing 1 to right click, 2 to move mouse, 3 to left click, 4 to move mouse back etc)
clickmouse2 will be replaced with clickmouse if it's too fast