Callback_listbox1 event to change content of another listbox2

I have a listbox1 with different items and when one of these items is selected (e.g project1) this item is used as a field structure name. Therefore the listbox2 is updated with the fieldnames of 'Database.project1', and example is shown below.

function listbox1_Callback(hObject, eventdata, handles)

project1 = get(hObject)%%takes selection item
load('Database.mat');%load Database structure
List = fieldnames(Database.(project1));%take fieldnames from Database.project1 structure
set(hObject.listbox2,'String',List);% update new items for listbox2

But this code is giving the next error:

Argument to dynamic structure reference must evaluate to a valid field name.

Any idea about how can be implemented?

Thanks in advance

[Jan]

And in which line does the error occur?

Answer 1

[Jan]

project1 = get(hObject)

seems to be incomplete. Do you mean:

string   = get(hObject, 'String');
value    = get(hObject, 'Value');
project1 = string{value};

[Manuel]

Now it detects perfectly the item selected, thanks a lot.

But when is going to check the fieldnames:

List2 = fieldnames(Database.project1);

I got the next error for this line:

Reference to non-existent field 'project1'.

I think is because is not taken the content of the variable project1 or also could be because project1 is a string and we are making reference to a cell, right? How could I solve that?

[Manuel]

Problem solve, just need to refer to the content of the variable by using ().

List2 = fieldnames(Database.(project1));