ahmedarain24

Based on the code you provided, it seems that you are trying to convert the value of `newent` to uppercase using the `strtoupper()` function. However, it appears that the uppercase conversion is not working as expected and accepting any character.
To properly convert the value to uppercase in JavaScript, you should use the `toUpperCase()` method instead of `strtoupper()`. Here's the corrected code:
```javascript
newent.value = newent.value.toUpperCase();
if (newent.value === 'B' || newent.value === 'P' || newent.value === 'T' || newent.value === 'D') {
    EnterSw.value = 0;
    return true;
} else {
    alert('INVALID HAND / MAIN INVALID');
    newent.select();
    return false;
}
```
With this modification, the `toUpperCase()` method will convert the value of `newent` to uppercase, and the subsequent comparisons will check against uppercase characters ('B', 'P', 'T', 'D').