You can control the content entered in a list sheet column, and the formatting of each cell in the column, from the Column Settings dialog box, which you display by double-clicking the column name. In the Column Settings dialog box, you can specify formatting appropriate to the type of data you expect the column to contain. For example, you can specify the number of decimal places to display, the symbol that appears before currency values, the way dates or times are displayed, and formatting criteria. You can specify a value to appear by default in all the cells in the column by selecting the Default Value check box and entering the value in the text box. You can prevent the entry of duplicate values by selecting the Unique Values Only check box.

You can format the contents of each list sheet column to match a pattern, and specify a default value.

To further restrict the content that can be entered into a column cell, click the Validation button to display the Data Validation dialog box.

You can prevent users from entering data that doesn’t fit specific criteria.

In the Data Validation dialog box, you can restrict the values that can be entered into a column cell. For example, you can specify that a date must fall within the current calendar year, that a number must be positive, that a text entry be no more than 30 characters, and other types of restrictions. If other people will be entering data in the list, you can inform them of the data entry restrictions by displaying an input message for each cell they select.