Simulink startfcn undefined function for input argument of type 'char'

Hello everyone, I am using some simulink/matlab to run a receiver and log some data. To do so I put the function to create, open and type the header in the StartFcn (and stopFcn to close) of the simulink model. Basically:

LogFileName = 'adsb_log.txt'; StartDataLog(LogFileName);

And in the same folder I have a file containing the 'StartDataLog' function. In itself 'StartDataLog' works fine, but when I call it in simulink the system is unable to process it:

Error evaluating 'StartFcn' callback of block_diagram 'Receiver003'. Caused by Undefined function 'LogstartDataLog' for input arguments of type 'char'.