active vibration control

[mz2009]

hi guys,
i have a problem with getting the displacement u in x direction using this coding :

*get,el,node,2,u,x

and a message of error is monitored in the solver output while solving:

The degree of freedom solution is not available.
Line= *GET, el, node, 2, u, x
The *GET command is ignored.

i hope anyone could really help me and thanks in advance