how to trace tcl variable incvi

now,I have some problems in labwindows\cvi.I use the cvi to make a UI. It was used to invoke a Tcl script which execute independent in a tcl file,and in cvi ,I want to trace the variable in tcl script.There is a C function called Tcl_Tracevar(interp,varName,flags,proc,clientData),can i use it in cvi to trace variable in tcl ?if not ,how can i trace the variable?