How to find midcrosseover points ?

Hello Friends, I am facing a problem in calculating the crossing points of a signal. for calculating crossover points i am using a matlab inbuilt function "Midcross(x,t)" but this function gives the exact crossover points if the signal having state level [1 0] or [1 -1] but i not getting the all crossover points if the signal has different amplitudes. For eg if my signal is of this type -

and if i use midcross for finding crossing points at 0.47 volts then i get only two crossing points. please help