trying.html

    <!DOCTYPE html>
    <html lang="en">
    <head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <style>
    .custom-input {
        display: none;
    }
    </style>
    <script>
    function optionChanged() {
        var selectedOption = document.getElementById("options").value;
        var customInput = document.getElementById("customInput");

        if (selectedOption === "custom") {
        customInput.style.display = "block";
        } else {
        customInput.style.display = "none";
        }
    }

    document.addEventListener("DOMContentLoaded", function() {
        document.getElementById("options").addEventListener("change", optionChanged);
    });
    </script>
    </head>
    <body>
    <label for="options">Select an option:</label>
    <select id="options">
        <option value="1000">Option 1000</option>
        <option value="2000">Option 2000</option>
        <option value="custom">Custom</option>
    </select>

    <div id="customInput" class="custom-input">
        <label for="customValue">Enter custom value:</label>
        <input type="text" id="customValue">
    </div>
    </body>
    </html>