You may want to use
coder.extrinsic('xlsread')
before you call xlsread in your block.
Additional tip: if your excel file is not changing dynamically, don't do this. Import all your data into workspace first before you start your simulation. What you are doing now is importing data from that excel file again and again, during every timestep. Also there are advanced methods now to import data from an excel file. Read about readtable, it saves you much time by also reading the column names from your excel file too, instead of reassigning every column to multiple variables, you could simply say, vehicle_data.vehicle_no
