Hi
use from below code . it is easy but work vey good.

def_path = ADDBS(JUSTPATH(FULLPATH(SYS(16,1))))
SET_def="set default to '"+def_path+"'"
&set_def

if your directory is C:\PROGRAM FILES\MY APP\ it work and if your database is in DATA directory only writ

set_dbf="set path to '"+def_path+"data'"
&set_dbf

and all thing work as well as posible.