How to add append string with .GetString ?

Hi, i need to read a char from specified position from string input like -> some_name.SetString("AAAA")
calling: status_input_position ("some_name", 1 )
return will be : 1

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int status_input_position ( SCString input_name, int input_position ){
SCString input_string = [input_name].GetString();
SCString position_status = input_string[input_position] ;
if (position_status == "A"){status_input_position = 1;}
return status_input_position; }

What i got from compiler :

error C3493: 'input_string' cannot be implicitly captured because no default capture mode has been specified
error C3493: 'input_position cannot be implicitly captured because no default capture mode has been specified
error C3493: 'status_input_position' cannot be implicitly captured because no default capture mode has been specified