You can put it into a worksheet open sub routine. See below.
Add the macro to the Thisworkbook sheet in the VBA editor.

Private Sub Workbook_Open()
'
' Macro1 Macro
' Macro recorded 2/28/2007 by Joel Warburg
'

'
Worksheets("Sheet1").Cells.Select
Selection.NumberFormat = "000000.00"
End Sub

"wrapumup" wrote:

I see several questions and answers on this. I know I can go to custom format
and for example put 00000.00 to get the display with leading zeros like I
want, but is there a way to make that be the default? I am sending this file
to a user and don't want to make them do this. Thanks.