I don't understand. Is FrameCallback(sender,args) your function or not, or if it's not your function but do you have the source code for it? It seems like you have it because you proposed some changed code for the inside of that function.
Anyway, what does that code have to do with some DLL that you're calling? If you're using loadlibrary() to load some vendor's DLL so that you can call it, then what does that have to do with FrameCallback()?
Anyway, it should work as long as you have a control called storing and you have access to handles. Either pass handles in to FrameCallback()
function handles = FrameCallback(handles, sender, args)
or try to find it using the code Geoff gave you. If you don't want to pass handles back out, you can call guidata() to update it instead.
Then you can use modern OOP syntax like this:
handles.storing.Visible = 'on';
handles.storing.String = sprintf('Storing %d.', getFrameCounter-1);
Anyway, I don't think any of that will help you with setting parameters internal to the DLL that are not exposed and you're not able to set by passing values into the DLL for them, because, as you say "it's buried in a dll so I can't change the parameters to pass". If the DLL is not willing to let you send in new values, then you are probably out of luck.
