dual monitors with a twist

so heres the thing

i have a lap top that can use an external monitor which works extremely well.

i have the desktop which the monitor is originally used for.
heres the twist to my question.

i do not have a kmv switch,but i do have a cord....i do not know what its called but the male ends allow me to plug an end into my monitor,and another end to either the desk top or laptop,and the regular cable that has just one male and female end.

with this cord i would like to be able to press a button so i could switch from having an extended laptop screen via monitor to checking my desk top

i tired to do this by hooking the cords up every way possible,i know this can work somehow but i need help.

does any one have any advice to avoid buying new components?

Can you get pics or links to the cord?