Writing to Excel spreadsheet with ASP.Net site using the Excel Javascript API

I have created an ASP.Net webapp using the Empty Template in Visual Studio 2017. The website has many familiar Web Controls such as Button (s), ImageButton, and Label (s). Users open a picture inside the ImageButton control and are able to click inside the control. The webapp calculates a value depending on where the user clicks in the ImageButton, and the values are displayed in the corresponding Label controls. The user is meant to write the values into an open Excel Spreadsheet (this is where the issue lies). For additional context, every action taken by the user is handled by a client-side javascript function-- with the exception of opening the picture. The opening action is handled by C# code belonging to the aspx page.

In the process of writing a similar Excel Web Add In, I found some very helpful code for writing to an Excel Spreadsheet using the Excel JavaScript API.

Here is that very code:

function HighlightCell() {
    Excel.run(function (ctx) {
                // Create a proxy object for the selected range and load its properties
                var sourceRange = ctx.workbook.getSelectedRange().load("values, rowCount, columnCount");
                var sheet = ctx.workbook.worksheets.getActiveWorksheet()
                // Run the queued-up command, and return a promise to indicate task completion
                return ctx.sync()
                    .then(function () {
                        var highestRow = 0;
                        var highestCol = 0;
                        var highestValue = sourceRange.values[0][0];

                        // Find the cell to highlight
                        for (var i = 0; i < sourceRange.rowCount; i++) {
                            for (var j = 0; j < sourceRange.columnCount; j++) {
                                if (!isNaN(sourceRange.values[i][j]) && sourceRange.values[i][j] > highestValue) {
                                    highestRow = i;
                                    highestCol = j;
                                    highestValue = sourceRange.values[i][j];
                                }
                            }
                        }
                        cellToHighlight = sourceRange.getCell(highestRow, highestCol);
                        cellToHighlight.format.fill.color = "IndianRed";
                        cellToHighlight.values = 5;

                  })
                  .then(ctx.sync);
         })
         .catch(errorHandler);

}

The code works like a charm within the Excel Web Add In, but it hasn't worked so far within the ASP.Net webapp. From my understanding, it is because the code hasn't been able to retrieve the active workbook / worksheet. This could be because of the disconnect between the server and the client-side from what I know.

Is there any way to open an excel spreadsheet on the client-side with javascript or C#. Can I even use the above code in an ASP.Net webapp?

EDIT: more code I opened the spreadsheet on the client side with this code:

function excload() {
    var selectedFile = document.getElementById('imgupload').files[0];
    document.getElementById("frame").src = window.URL.createObjectURL(selectedFile);
}

In this code, imgupload is an HTML file input and "frame" is an iframe element. I'm not sure why when I run it, instead of just opening the spreadsheet in the iframe, it opens the spreadsheet in a new instance of the Excel program on the computer.

Noticed something weird in writing code: Calling the function HighlightCell--which writes to the cell refreshes the page, while none of the other javascript functions do. This happens even if I add a return false; line to the function and call it from button with _onclick ="HighlightCell(); return false;"

REDUX of "Noticed something weird in writing code":

Managed to call Highlight cell without refresh by using:

$(document).ready(function () {
        $('#chosen').click(HighlightCell);
    });

But still no writing takes place