An array for multiple LHS assignment cannot contain expressions

so I am trying to using matlab to control keithley sourcemeter, and I am trying to do a voltage sweep. The function given by the instrument is

[READING]=invoke(OBJ,'performsweepvi',RANGING,SPACING,DIRECTION,SOURCECOMPLIANCE,SOURCEPROTECTION,START,STOP,NUMBEROFPOINTS,SENSERANGE,SPEED,READING)

I put in the necessary value on the right hand side and when I execute it, it responds that An array for multiple LHS assignment cannot contain expressions. So I am not sure what to do. I have removed the bracket and another error shows up where it needs a logical or numerical value.