By default, Excel doesn’t show any error even when somebody begins typing a customized worth on the dropdown cell. However, you may alert them with an error message to forestall it. Upon the Data Validation immediate, choose the Error Alert tab.Enable Show error alert after invalid information is entered checkbox.Provide a title and error message you need to show upon customized enter.Choose one of many following choices below the Style subject. Stop: It doesn’t enable the person to enter an invalid worth. (solely takes legitimate worth).Warning: It shows a warning immediate the place customers can select to stay with the worth they entered or re-enter a legitimate worth.Information: It shows the error message, however customers can proceed inputting any worth they need. Additionally,  you may pre-inform the person about the kind of values they're anticipated to enter with the assistance of a show message. Select the Input Message tab.Tick Show enter message when cell is chosen checkbox.Then, enter a title and the message you need to show when the person tries to enter a worth. Click OK.Now, you get somewhat pop-up message whenever you hover over the cells with dropdown values.