is there a script that i can assign a selected track in pro tools to a specified fader number

I don't have a EUCON device here to test with, but try this:

function assignSelectedTrackToFader(faderNum) {
    var faderIndex = faderNum - 1;

    var eucon = sf.ui.app('com.Euphonix.EuControl');
    eucon.appActivate();
    eucon.getMenuItem("Window", "EuControl Settings").elementClick();

    var win = eucon.windows.whoseTitle.is('EuControl Settings').first;
    win.elementWaitFor();

    //Switch to Assign tab
    win.tabGroups.first.radioButtons.whoseTitle.is('Assign').first.elementClick();
    win.tabGroups.first.checkBoxes.whoseTitle.is('Display Application\'s Track Numbers').first.elementWaitFor();

    //Clear existing assignments
    win.tabGroups.first.buttons.whoseTitle.is('Clear All Assignments').first.elementClick();

    //Init
    var table = win.tabGroups.first.scrollAreas.first.tables.first;
    var rows = table.childrenByRole("AXRow").allItems;
    var selectedTrackName = sf.ui.proTools.selectedTrackNames[0];

    //Assign tracks
    var row = rows[faderIndex];
    if (!row || !row.exists) throw `Couldn't find fader ${faderNum}`;

    //Select row
    var cells = row.children.allItems;
    cells[cells.length - 1].popupMenuSelect({
        menuPath: [selectedTrackName]
    });
}

assignSelectedTrackToFader(1);

You can change the fader number to assign the selected track to in the last line.