应xie0909的要求，做了个限次实例，只用了几行的语句，不是很困难。（当然，你也可以加入其它功能，如通过进度条来显示）

不能下载。

日期限制：
windir:=baSysFolder("windows")
if FileType(windir^"\\d.lim")=0then
WriteExtFile(windir^"\\d.lim","symbol")
baWriteRegNumber("datelimit","year","year","HKEY_CURRENT_USER")
baWriteRegNumber("datelimit","month","month","HKEY_CURRENT_USER")
baWriteRegNumber("datelimit","day","day","HKEY_CURRENT_USER")
else
year1:=baReadRegNumber("datelimit","year",0,"HKEY_CURRENT_USER")
month1:=baReadRegNumber("datelimit","month",0,"HKEY_CURRENT_USER")
day1:=baReadRegNumber("datelimit","day",0,"HKEY_CURRENT_USER")
datelimit:=(Year-year1)*365.5+(Month-month1)*30.5+(Day-day1)
if (datelimit<0|datelimit>=3)then
baMsgBox("过了日期","警告","OK","exclamation",0)
Quit(0)
end if
end if

次数限制：
times:=baReadRegNumber( "Keyname", "used times" ,0,"HKEY_CURRENT_USER")
if times=0 then baWriteRegNumber( "Keyname", "used times" ,1,"HKEY_CURRENT_USER")
else
times:=times+1
baWriteRegNumber("Keyname", "used times" ,times,"HKEY_CURRENT_USER")
end if
if times>3 then
baMsgBox("使用次数过期","警告","OK","exclamation",0)
Quit(0)
end if

错了，是budapi.u32

我有，过几天发上来！