Cant disable key with xmodmap

my f3 key sometimes randomly stuck. so i tried to disable it

here from xev

eyPress event, serial 28, synthetic NO, window 0x5400001,
    root 0x57f, subw 0x0, time 1894743, (254,214), root:(848,506),
    state 0x0, keycode 69 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XmbLookupString gives 0 bytes: 
    XFilterEvent returns: False

KeyRelease event, serial 28, synthetic NO, window 0x5400001,
    root 0x57f, subw 0x0, time 1894911, (254,214), root:(848,506),
    state 0x0, keycode 69 (keysym 0x0, NoSymbol), same_screen YES,
    XLookupString gives 0 bytes: 
    XFilterEvent returns: False

and then i run this

xmodmap -e "keycode 69 = NoSymbol"

it doesnt work

same as this

xmodmap -e "keycode 69 ="

please help

Your ~/.Xmodmap file should have

keycode 69 = NoSymbol

in it … Not quite sure i follow what you want to do, change the behavior of that key on the fly?