[Closed] bone rotation expression

i’ve this leg/foot sistem

now, I want lo set rotation for the last leg’s bone (selected in image) half between foot control and knee. so I set an expression controller for x rotation: (footcontrol.xrotation/2)+ degtorad(IKchain.swivelangle/2)
the footcontrol.rotation seems to work, but i’ve problem with swivelangle thet seems to ignore the expression and put the entire value of angle. so I’ve used the value of a custom attribute that controls the swivel angle and it works fine.
the expression is : (footcontrol.xrotation/2)+ degtorad(knee/2) but when i tried to make it by maxscript assigning the knee value by “addscalartarget” it return the error:target needs to be controller or subanim. What can I do? it’s not a constant or vector