I am trying to make this:

A player walks up to a poster, when player hits a key(predefined) a mouse pointer shall appeare.So you can click the poster and a panel comes up. Then you use the mouse pointer to click buttons on panel. When finished bouth panel and mouse pointer is hidden again.

example:
if(key_h)
{some code to get the mouse pointer show}

Where do I put the code for the mouse pointer?
In the player code?
In the function or action that calls the panel whit buttons?
In the main code?
Or do I make a code page of its own, and just call it from there?

There are many ways to do this.
But, it makes sense to use a global variable to make differences of global states: state_poster, state_running_around, state_menu etc..

In a main function you can run a while loop where you switch between the states and run the depending functions.

Pseudo code:

function general_states

while

if key_h && general_state == state_running_around

general_state = state_poster
mouse_mode = 1;
mouse_pointer = 1;
mouse_map = arrow_bmp;


if general_state == state_poster

mouse_pos.x = mouse_cursor.x;
mouse_pos.y = mouse_cursor.y;

if key_h && general_state == state_poster

general_state = state_running_around
....

Yes, that looks like a good solution. I will try it and see how it works for me.

So many ideas to try, and to litle hours in the day......