これならどーだ!
sdim MS,65536
mesbox MS,200,200,1,0
hEdit=objinfo(stat,2)
button gosub "get",*get
repeat
sendmsg hEdit,0x000E,0,0
size = stat
wait 1
title "" + size
loop
*get
sendmsg hEdit,0x000E,0,0
size = stat
sdim buf,size+1
sendmsg hEdit,0x000D,size+1,varptr(buf)
dialog strlen(buf)
return