How to add user specified items to OPC data group - matlab

Question

I am creating a MATLAB application which connects to an OPC Server and reads the Tag properties. The MATLAB documentation is telling me that I can add a group, add tag items, and then read the value:
grp = addgroup(da, 'ExRead');
itm = additem(grp, 'Tag.Argument');
The problem is that I don't know the tag argument, in my app the user is selecting an available tag in a popupmenu and the value is written to a string, but when I call:
val = get(handles.popupmenu1, 'Value'); // Ask for Value selected item
string_val = get(handles.popupmenu1, 'String'); // Ask for string
stringName = string_val{val}; // Ask for string corresponding to the specified value
set(handles.text1, 'String', stringName); // Display the selected tag
item1 = additem(Group1, stringName); // Add the selected string to a global group "Group1"
read1 = read(Group1, item1); // Read the value
set(handles.text11, 'String', read1); // Display the value
But when I run the code MATLAB generates errors. I guess the problem is item1 = additem(Group1, stringName); In all the MATLAB documentation examples I see something like item1 = additem(Group1, 'adres.adres.1'); This should explain why I am unable to add any data to the Group1.
But how can I add an item to a taggroup which must be specified/selected by a user?

Answer 1

Group1 appears to be a variable here, that is undefined. Perhaps you meant to type 'Group1', with quotes? That would add item to a group called Group1.

Answer 2

If I get it right, you don't know which tag names you should use.
The correct ItemID (Tag name) is typically found by browsing the server address space.
Before you implement browsing in your application (if possible with MATLAB), you can use test clients, such as Prosys OPC Client to browse the address space and find the proper ItemID(s) to use.