1. Select the range that you will limit date entries with specify character length.

2. Click the Data validation in the Data Tools group under Data tab.

3. In the Data Validation dialog box, select the Text Length item from the Allow: drop down box. See the following screen shot:

4. In the Data: drop down box, you will get a lot of choices and select one, see the following screen shot:

(1) If you want that others are only able to entry exact number of characters, says 10 characters, select the equal to item.
(2) If you want that the number of inputted character is no more than 10, select the less than item.
(3) If you want that the number of inputted character is no less than 10, select the greater than item.

4. Entry exact number that you want to limit in Maximum/Minimum/Length box according to your needs.

5. Click OK.

Now users can only enter text with limited number of characters in selected ranges.

Easily prevent from typing special characters, numbers, or letters in a cell/selection in Excel

With Kutools for Excel's Prevent Typing feature, you can easily limit character types in a cell or selection in Excel.

The Data Validation allows us to set input message for text length limitation besides selected cell as below screenshot shown:

1. In the Data Validation dialog box, switch to the Input Message tab.

2. Check the Show input message when cell is selected option.

3. Entry the message title and message content.

4. Click OK.

Now go back to the worksheet, and click one cell in selected range with text length limitation, it displays a tip with the message title and content. See the following screen shot:

Another alternative way to tell user the cell is limited by text length is to set an error alter. The error alert will be shown after you entry invalid data. See screenshot:

1. In the Data Validation dialog box, switch to the Error Alert dialog box.

2. Check the Show error alert after invalid data in entered option.

3. Select the Warning item from the Style: drop down box.

4. Input the alert title and alert message.

5. Click OK.

Now if the text you entered in a cell is invalid, for example it contains more than 10 characters, a warning dialog box will pop up with preset alert title and message. See the following screen shot:

One click to prevent from entering duplicate data in a single column/list

Comparing to setting data validation one by one, Kutools for Excel's Prevent Duplicate utility supports Excel users to prevent from duplicate entries in a list or a column with only one click.