ciao, potresti fare come indicato qui http://blogs.ugidotnet.org/mb/archive/2008/09/03/utilizzare-un-controllo-textbox-come-finestra-di-log.aspx
cioè :
private const string cStrCarReturnLnFeed = "\r\n";
int PosToRemove = txtLog.Text.LastIndexOf(
cStrCarReturnLnFeed,30);
txtLog.Text = txtLog.Text.Substring(
PosToRemove + cStrCarReturnLnFeed.Length);
Ciao.
Nicolas
http://perledinico.blogspot.com