Didn’t this work? 

It's not the same topic. That question was about deducting the amount spent from the net income. This question is about the amount spent not being more than the net income.

​@O.kisa,

Is your spending question and Constant Sum question? If so, as long as there is no display logic on the Constant Sum choices, you don’t need JS. Use custom validation where the first choice is less than the spending limit minus all the other choices. For example:

$e{ e://Field/SpendLimit -  q://QIDx/ChoiceNumericEntryValue/2 - q://QIDx/ChoiceNumericEntryValue/3 } 

Where QIDx is the QID of your constant sum question.

$e{ e://Field/SpendLimit -  q://QIDx/ChoiceNumericEntryValue/2 - q://QIDx/ChoiceNumericEntryValue/3 } 

No, It did not work. But thank you.

I do use the code below. If it is not problem for you, could you please check it?

Thank you in advance. 

Qualtrics.SurveyEngine.addOnReady(function () {
    const quest = this;
    const qc = quest.getQuestionContainer();

    // Get the Net_Income value from Embedded Data
    const maxAmount = parseFloat(Qualtrics.SurveyEngine.getEmbeddedData("Net_Income"));
    const alertText = "Please ensure the amount consumed is less than";

    const nextButton = document.querySelector("#NextButton");

    // Add a row below the total row
    const totalRow = qc.querySelector("tr.CSTotal");
    const remainingRow = totalRow.cloneNode(true);
    totalRow.insertAdjacentElement("afterend", remainingRow);

    // Give the total rows new labels for clarity
    totalRow.querySelector("th").innerHTML = "Amount Consumed";
    remainingRow.querySelector("th").innerHTML = 'Amount Left <small id="amountAlert" style="color: red;display:none;">+++++ $ _____.</small>';

    const totalInput = totalRow.querySelector("input");
    const remainingInput = remainingRow.querySelector("input");

    // Monitor changes to the total
    totalInput.oninput = function () {
        setTimeout(() => {
            // Ensure we are parsing the value correctly as a number, and prevent non-numeric input
            let amountUsed = parseFloat(totalInput.value.replaceAll(/\D/gm, ""));  // Remove non-numeric characters

            // If the input is not a valid number (NaN), set it to 0
            if (isNaN(amountUsed)) {
                amountUsed = 0;
            }

            const amountLeft = maxAmount - amountUsed;

            // Update the remaining total with the amount left
            remainingInput.value = amountLeft;

            // If amountLeft < 0, disable the Next button and show the alert message
            if (amountLeft < 0) {
                // Disable the Next button and prevent page transition
                nextButton.disabled = true;  // Disable the Next button
                Qualtrics.SurveyEngine.setNextButton(false);  // Prevent moving to the next page
                alertMessage.style.display = "block";  // Show the alert message
            } else {
                // If valid, enable the Next button and hide the alert
                nextButton.disabled = false;  // Enable the Next button
                Qualtrics.SurveyEngine.setNextButton(true);  // Allow moving to the next page
                alertMessage.style.display = "none";  // Hide the alert message
            }
        }, 0);
    };

    // Start with the entire amount being available
    remainingInput.value = maxAmount;

    // Insert values into the alert message
    const alertMessage = qc.querySelector("#amountAlert");
    alertMessage.innerHTML = alertMessage.innerHTML.replace("+++++", alertText);
    alertMessage.innerHTML = alertMessage.innerHTML.replace("_____", maxAmount);
});

$e{ e://Field/SpendLimit -  q://QIDx/ChoiceNumericEntryValue/2 - q://QIDx/ChoiceNumericEntryValue/3 } 

It works. You must have done it incorrectly.

$e{ e://Field/SpendLimit -  q://QIDx/ChoiceNumericEntryValue/2 - q://QIDx/ChoiceNumericEntryValue/3 } 

Is it true ?

$e{ e://Field/SpendLimit -  q://QIDx/ChoiceNumericEntryValue/2 - q://QIDx/ChoiceNumericEntryValue/3 } 

When I use custom validation, it gives an error even when I spend less than the net income.

You need to provide more details - a survey preview link, your question structure, how will the choices be made etc.

Here is the link: https://tilburgss.co1.qualtrics.com/jfe/preview/previewId/3b01a810-1a59-4458-9be6-dc7b05262950/SV_0U7WCRd4Rz1gtU2?Q_CHL=preview&Q_SurveyVersionID=current

Now I see - it isn’t a Constant Sum. I happen to offer a function that does this.