I tried INTRPT CMD with my 3458A (ACAL DCV) and it works ok. No problem.
I also looked up the manual for the 34465A, there are various CAL commands in the sub-set.
If you are logging VDC then you only need to autocal ADC, i.e.:
CAL:ADC?
This would be faster.
I have a 34461A and although it doesn't support autocal I tried sending:
CAL:ADC?
The meter displayed an error "Calibration step failed......", which is fine, but then the meter stopped updating it's display, and won't only resume if I hit a key on the meter. Not good!
So, with this meter it looks like if there is an issue, or you don't send the right command properly then the meter hangs till you press a key. Maybe there is a GPIB command to restart?
In saying all that, you mentioned you are using the command:
*CAL?
In the manual it specifies that this command performs autocal and returns the result. So there is your problem, *CAL? is not a SEND ASYNC command, it is a QUERY ASYNC command and so will not work with INTRPT CMD.
You need to find a CAL command that is SEND ASYNC, i.e. does not expect to send a reply......with the current version of WinGPIB.
Or, you can STOP logging, send a manual QUERY ASYNC command, wait till it finished, and then manually RUN logging again.
Ian.
EDIT: Corrections made to above.