This is not supported in the BMP5 Direct SDK. The options available are to specify a starting record number, get the most recent record, or collect all available records. When specifying a starting record, all data from that record forward is then retrieved. The burden is on the programmer that uses the SDK to keep track of the last record number retrieved within the program and then to retrieve what is needed or desired in the future.
The functionality to specify a date/time data collection range is available in the LoggerNet-SDK and the LoggerNet Server SDK. Both the LoggerNet-SDK and the LoggerNet Server SDK are available for purchase from Campbell Scientific.