I'm having problems running this GUI

Undefined operator '*' for input arguments of type 'cell'.

Error in FIN_EFFICIENCY>pushbutton1_Callback (line 119)

per=pi*d;

Error in gui_mainfcn (line 95)

feval(varargin{:});

Error in FIN_EFFICIENCY (line 43)

gui_mainfcn(gui_State, varargin{:});

Error in

matlab.graphics.internal.figfile.FigFile/read>@(hObject,eventdata)FIN_EFFICIENCY('pushbutton1_Callback',hObject,eventdata,guidata(hObject))

Error while evaluating UIControl Callback.

[David Marcel-Ihekweme]

I keep getting these errors, I'd really appreciate a fix.