How to measure a time difference in miliseconds?

Hi,

I'ld like to measure a time difference (in miliseconds) between two operations. How to get a current time in milliseconds?
for example

Code:

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int microStart = function_time_in_miliiseconds();
operationr1();
int microEnd = function_time_in_miliiseconds();
ind difference = microEnd-mircoStart;

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thanks

Code:

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QTime time;
time.start();
// operation
int difference = time.elapsed();

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Thank you, that's what i'm saying :)