I have invisible IFRAME (named server_commands) in a HTML page.

I need a callback to send modified XML data island (current document rows) to server for price calculation.

For this, I use the command

document.all.server_commands.src="Calculate?Data="+
   escape(DocHead.documentElement.xml);

However, if xml data is some thousands of bytes, IE does not send
any data to server: its navigation icon in upper right corner
animates, but no data is sent to web server.
Why ?

If I use small query string, all works OK. I tried to use POST request but this seems to be impossible: it seems that it is not possible to assing data to form inside IFRAME and submit() this.