You will need to do this in the callback of your button.
Assuming that when you create the button, you had set the text to Play and set the Icon file to play icon image.
function ButtonDownFcn(app,event)
switch app.Button.Text
case 'Play'
% do something to play
% change the text and icon
app.Button.Text = 'Pause';
app.Button.Icon = 'Pause.png'; % path to image file
case 'Pause'
% do something to pause
% change the text and icon
app.Button.Text = 'Play';
app.Button.Icon = 'Play.png'; % path to image file
end
end
