Hi,
If it is just for display purposes, format the cell with this custom type:
#-###-##-###-#
If you really need to have the hyphens within the value then you could use a formula such as:
Code:
=LEFT(A1)&"-"&MID(A1,2,3)&"-"&MID(A1,5,2)&"-"&MID(A1,7,3)&"-"&RIGHT(A1)
Hope that helps...