[ns] How to call a procedure after a constant delay

[Somera Javed]

Hi,
i  am trying to call a procedure after a delay of every 0.01 sec

proc loop {} {
        global abc value
        set value [$abc get_value]
        exit 0
}
set time 0.2
set inc 0.01
while 1 {
    $ns at $time "loop"
    set time [expr $time + $inc]
    if {$value == 1} break;
}

but the program stuck while execution
what is the right way to do this???