Hi Matt,
I've found a bit of information on this and I reakon it should be possible although fairly difficult. Unfortunetly there is nothing definite on our website or on the HP website.
First of all, the following link has the user manual on there and a link to e-mail their Technical Support. I've sent you this as I can't really advise too much on the HP IPAQ side of things as I don't know how they work.
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?product=425750〈=en&cc=us&lc=en&dlc=en&
What you will need to do is find either the dll which controls this operation, or the function which you can then create into a dll and you can then have this called in your LabVIEW code.
The following discussion forum looks at turning the screen off while doing operations and this is about as close as I could find to your application.
http://forums.ni.com/ni/board/message?board.id=170&message.id=87400&requireLogin=False
In here someone has said it is possible by calling the function in a dll and then calling that dll in LabVIEW but unfortunetly they couldn't get it to work properly and it is obviously a hard operation to perform.
If you have any further questions then please get back to me and I will be more than happy to help out.
Best regards,
Peter H.
Applications Engineer.
NIUK.
