DeleteNumberFormat Method [Excel 2003 VBA Language Reference]
Deletes a custom number format from the workbook.
expression**.DeleteNumberFormat(NumberFormat)**
expression Required. An expression that returns a Workbook object.
NumberFormat Required String. Names the number format to be deleted.
Example
This example deletes the number format "000-00-0000" from the active workbook.
ActiveWorkbook.DeleteNumberFormat("000-00-0000")
Applies to | Workbook Object