Many thanks Pete for your response.
I have resolved the issue by using the following suggestion by an Avsim member.
"Open the Axis Assignment tab in FSUIPC.
Click the 'rescan' button and move the condition lever, that should change the value in 'joy#' and 'Axis#' to show FSUIPC has identified the control you moved.
In 'Type of action' select 'Send to FS as normal axis', tick the first box and from the list select 'Axis Mixture Set'. That should set the condition lever to act as a mixture control, all you need to do then is calibrate it in the 'Joystick Calibration' tab.
Also note that you can, if you wish, make that axis assignment specific to the current aircraft or to all aircraft."
Regards Richard