resize text field in crystal report before sending content

hi all
i have a crystal report text field that i want set length to 10 character ..
it is used for show name+family in report

i want when this field cant show all character of name+family , font size reduce for 1 unit , until field can show name+family compelete ...

for example :
this field can show only 10 character
and 
in database exists one filed that have 15 character length
now
this filed should reduce font size until can show all 15 character of field

how do i this ?

please help me

thanks a lot

Tags: C#, CrystalReports, Reporting