MilliSecondsBetween returns the number of milliseconds between two specified TDateTime values.

The ordering of the two dates doesn't matter - the number of seconds will not be negative.

Declaration: Function MilliSecondsBetween(const ANow, AThen: TDateTime): Int64;

A simple example follows.

procedure OnMapEvent(var Value:Variant);
var
TheDate, ThatDate : TDateTime;
NumBetw : integer;
begin
//Result is 999 milliseconds
TheDate := EncodeDateTime(2023, 02, 13, 10, 00, 00, 000);
ThatDate := EncodeDateTime(2023, 02, 13, 10, 00, 00, 999);
NumBetw := MilliSecondsBetween(TheDate,ThatDate);
LogInfo('The number of milliseconds between these dates is - '+IntToStr(NumBetw));
end;