There are examples available for this,
Automatic Analog Feedback with FlexMotion - Example - Development Library - National ...
Onboard Analog Input Using Return Data Buffer - Flexmotion - Example - Development ...
Onboard Analog Input Using General Purpose Buffer to Pass Data to Host - Flexmotion - ...
Master Analog Input - Slave Axis Gearing.vi - Example - Development Library - ...
if you type the above titles into search at ni.com/support you'll get them, http://search.ni.com/query.html?col=alldocs&layout=Example&qp=ContentType:Example&qt=%2Bmotion+%2Blabview+analog+input
This could be a plain LV (not motion) programming issue too, refer,
http://zone.ni.com/devzone/conceptd.nsf/2d17d611efb58b22862567a9006ffe76/d2e196c7416f373a862568690074c759?OpenDocu
ment
http://digital.ni.com/public.nsf/websearch/328E616C0237A23386256AE1005D87A1?OpenDocument