Error Message in uitable GUI

I have a editable uitable in a GUI. How can I check the user input data, and if the values are negative, display an error message?

Answer 1

[Adam]

There's a CellEditCallback in which you can add whatever code you want in response to someone entering something in a cell of the table.

[laurie]

if any((data(:,1)) < 0)==1
    warndlg('Must be greater than zero.','Warning!')
end

Where (data(:,1)) is column 1 of my uitable

I get the error:

Undefined function 'lt' for input arguments of type 'cell'.

[Adam]

Isn't 'data' a cell array from a uitable? In which case you need to apply cell operations or convert to a numerical array if it is pure numbers