SONWriteRealBlock

  SONWRITERealBLOCK writes data to an Real channel

  RET=SONWRITERealBLOCK(FH, CHAN, BUFFER, COUNT, STARTTIME)
  INPUTS: FH the SON file handle
          CHAN the target channel
          BUFFER the data to be written (single floating point)
          COUNT the number of data items to write from buffer
          STARTTIME the time of the first sample in buffer (in clock ticks)

  RET is the time for the next sample to be supplied in a subsequqnt call to
  SONWRITERealBLOCK (assuming continuous sampling) or a negative error code.

  Fo efficient use of disc space, COUNT should be  a multiple of 
  (BUFSIZE - 20 bytes)/4 , where BUFSIZE is supplied in a prior call to
  SONSETRealCHAN (20 is the size of the block header on disc)

  see CED documentation

  Author:Malcolm Lidierth
  Matlab SON library:
  Copyright © The Author & King's College London 2005-2006