i just realised on my sheet that with the above formulae its giving me error

S-1
2012 figures = 0 (D10)
2013 figures = 34,000 (F10)

it should show 100% increase in expense but it's giving me "-". the forumale i am using

=IF(ISERROR((F10-D10)/D10),"-",(F10-D10)/D10)

i also tried this formula, but still "-"

=IF(ISERROR((F10-D10)/D10)=TRUE,"-",(F10-D10)/D10)

help please thanks