Similar command "ibsad" in VISA

[yangroot]

I have a PCI-GPIB card and want to use VISA instead of IEEE488.2 to play with an old telescope.

In my case, the secondary address must be configured frequently.

Could not find  command in VISA similar to ibsad.

Only know in viOpen, I can apply the secondary address (see below value "101" )

viOpen(defaultRM, "GPIB0::18::101::INSTR",VI_NULL,VI_NULL,&vi);

 But if want to other address, I must close and reopen again.

I do not think this is a good idea.

Thanks for any tips!!

[yangroot]

ViUInt16 sAdd;
sAdd=18;
viSetAttribute(vi,VI_ATTR_GPIB_SECONDARY_ADDR,sAdd); 

Just got one solution, hope it's correct!!

[yangroot]

It seems not working with above solution!!

Could somebody please tell me what is the difference between?

GPIB Bus Interface (INTFC) Resource

and 

Instrument Control (INSTR) Resource

Because in INTFC,  

VI_ATTR_GPIB_SECONDARY_ADDR

is RW, but in INSTR is RO(read-only).

Here, in my project, I can not change it.