Passing a variable from C++ to TCL

Hi Ns-Users , I am working on NS-2.35 and My work is about controlled
mobility for wireless sensor networks . I implement an algorithm to control
the mobility of the sink in C++ . at the end I need to send the new X and Y
positions of the sink to TCL to move the sink . Is there any function
needed for sending these variables to TCL? I just made a binding like this:

bind ("x-axis",&x-tcl)
bind("y-axis",&y-tcl)

but when I use them in TCL in the setdest i got an error message saying :
can't read x-axis and y-axis.
Can anyone help me please?