{
{    The purpose of this request is to calculate the difference between two
{ date times, convert the result to microseconds (us) and add in a base
{ free-running clock value.
{
{       JMP$CONVERT_DATE_TIME_DIF_TO_US (BASE_DATE_TIME, DATE_TIME,
{             CURRENT_CLOCK_TIME, FREE_RUNNING_CLOCK_VALUE);
{
{ BASE_DATE_TIME: (input)  This is the base date-time value used for
{       calculation of the date-time difference.
{
{ DATE_TIME: (input)  This is the date-time value used for calculation of the
{       date-time difference.
{
{ CURRENT_CLOCK_TIME: (input)  This is the relative clock time to be added to
{       date-time difference.
{
{ FREE_RUNNING_CLOCK_VALUE: (output)  This is the microsecond (us) value that
{       represents the difference in the date-times (in us) and the current
{       clock time that was specified.
