InitUsageCode
procedure InitUsageCode (const Key : TKey; Count : LongInt; Expires : TDateTime; var Code : TCode);
InitUsageCode creates and initializes a usage code using Key, Count, and Expires.
Count is stored as part of the Code.
The resulting code is valid until the internal Count is 0 or the date stored in Expires is reached.
This routine is defined in the OnGuard unit. (as of 1.15 this routine has been moved to the OgUtil unit)