Is it possible to make matlab wait for a live user input on excel (opened with ActiveX)?

Is it possible to make matlab wait for a live user input on excel (opened with ActiveX)? For example, assume the excel sheet is initially empty. If the user enters something in cell A1, matlab calculates something based on that value and punches it in in cell B1. Then the user enters something in A2, matlab calculates in B2, and so on.

Below is part of the code I wrote.

--------------------------------------------------

    startTime = tic;
    elapsedTime = toc(startTime);
    i = 1;
    while i < 5
        % READ VALUES
        sheet = 'Sheet1';
        inputRange = ['A' num2str(i)];
        while elapsedTime < 100
            [data, text, rawData] = xlsread1(fileName,sheet,inputRange);
            if ~isempty(data)
                disp('read value');
                break;  % Exit from the loop since they entered something.
            end
            elapsedTime = toc(startTime);
        end
        %WRITE VALUES
        myCalc = data^2; %CALCULATIONS YOU WANT
        outputRange = ['B' num2str(i)];
        xlswrite1(fileName, myCalc, sheet, outputRange);
        i = i+1;
    end

--------------------------------------------------

While matlab is waiting for a value in the cell A1, when I (i.e. the user) try to interact with the excel file and punch in a number in A1, it gives me the following error.

Error: Object returned error code: 0x800AC472

Error in xlsread1 (line 246)

    Excel.DisplayAlerts = 0;

Error in FactSage_Matlab_Macro (line 69)

            [data, text, rawData] = xlsread1(fileName,sheet,inputRange);

I'm using "xlsread1" and "xlswrite1" function from the links below.

www.mathworks.com/matlabcentral/fileexchange/22365-function-for-faster-data-transfer-matlab-%3C-%3E-excel

www.mathworks.com/matlabcentral/fileexchange/10465-xlswrite1

[Walter Roberson]

Continues http://www.mathworks.com/matlabcentral/answers/312220-how-to-make-matlab-wait-for-a-value-to-be-input-in-an-empty-excel-cell

Answer 1

[Guillaume]

While you could indeed poll excel through activex and see if a cell has changed, I don't think you can do it with xlsread (or a variant of it) since it requires that the excel file of interest be closed.

In any case, polling is a waste of CPU when excel has events you can listen to and wait for:

excel = actxserver('Excel.Application');  %start excel
excel.Visible = true;                     %make excel visible so user can interact
workbook = excel.Workbooks.Add;           %create a new workbook
worksheet = workbook.Worksheets.Item(1);  %get 1st worksheet
registerevent(worksheet, {'Change', @(~, ~, range, ~, ~) fprintf('Range %s was changed\n', range.Address)});
%each time a cell is edited the event is fired

Documentation for excel change event

Thoroughly lacking matlab documentation for handling COM events

[Kota Matsuo]

Thank you for your answer Guillaume. Wow I never knew about these excel events. I'll try it out! :)

Answer 2

[Walter Roberson]

No, it is not possible.

In Excel you could create a macro with MsgBox or InputBox to pop up a box that waited for input and then write that input into a cell and then use a MATLAB Engine call to trigger some action. However, there is no Excel operation corresponding to "wait for something to be input at such-and-such a location".

The closest you can get is to poll the location checking to see if something is there. Which is the approach Image Analyst described to you in your previous question http://www.mathworks.com/matlabcentral/answers/312220-how-to-make-matlab-wait-for-a-value-to-be-input-in-an-empty-excel-cell

There is a possibility that you might need to close down the Excel connection to the spreadsheet after every poll; I do not know. Also I do not know if you would need to "save" the spreadsheet before the contents were visible externally.

I see a suggestion that the particular error you are getting might be associated with attempting to access a cell while an excel dialog is popped up.

[Guillaume]

Huh? Excel has plenty of events that you can listen to.

[Walter Roberson]

Ah. I did not find those when I looked for information.

[Kota Matsuo]

Thank you for your answer Walter Roberson. As you suggest, if I wanted to do polling through activex, I might have to close excel after every poll. Maybe I can add a txt file to tell matlab when the next poll happens (e.g. write "1" in the text file when the user changed a cell in excel, or something close to that).