Map-clicks are local to the computer where the click happened. You would have to pass the resulting map position back to the server, via the publicvariable command.
Publicvariable does not work with arrays so you would have to separate the mapclick position into x and y components and then pass those back to the server separatly.
x=_mappos select 0;publicvariable "x"
y=_mappos select 1;publicvariable "y"
You need a script running on the server only that checks for these variables and then acts upon them accordingly.
There may be a better way to do this, this is just one way.