From: Andy F. on
So are you trying to wait until all of the information reaches the port before reading?  What you may try to implement would be to put the Number of Bytes Property Node in a while loop along with a slight delay.  The exit condition for this while loop could be when the number of bytes stop changing from one iteration to the next.  Once this happens you can then read all the bytes at port with a VISA read. 
Hope this helps!
Andy F.
From: lll on
Dear Andy ,
I will try to do it in your way. its sound promissing.I only need to put the Visa-Read outside the loop that i already have, its simple.
Thanks for you help.