The regular expression given to this property will be used during validation of the cell values in the column. As the user attempts to move the input focus out of the cell, the text in the cell will be validated against the regular expression. For the validation to succeed, all of the text in the cell must constitute a single match. If the cell contains a match and other characters then the validation will fail. For example, if the regular expression is "\d{2}" (meaning, two consecutive digit characters) and the cell's text is "12" then the validation will succeed. However, if the cell's text is "123" then the validation will fail because of the extra digit ("3") that follows the match ("12"). This behavior can be altered by appending or prepending ".*" to the regular expression, meaning that any number of characters can precede or follow the target match.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2