Hi Kaputa,

=IF(D30,LOG(C3/F3),""&TEXT(LOG(C3/10),"0.0"))

Ed Ferrero
Microsoft Excel MVP
http://www.edferrero.com

=IF(D30,LOG(C3/F3),""&LOG(C3/10)) gives me the two options that I want.
Thanks to all who responded. Now, the first part is rounded to 1 decimal
place, ie 0.0, because I chose so in custom mode. When the second part is
true, however, I loose the custom formatting and get several decimal
places
added. How do I prevent this?