Remove digital signature

[romBik]

Hello!

I need your help! The problem is:
The user signs the form section, then it is needed to unsign form
programmatically. I use this technique:

if (this.Signed)
{
IEnumerator num1 = this.SignedDataBlocks.GetEnumerator();
while (num1.MoveNext())
{
SignedDataBlock sdb = num1.Current as SignedDataBlock;
IEnumerator num2 = sdb.Signatures.GetEnumerator();
while (num2.MoveNext())
{
Microsoft.Office.InfoPath.Signature sig = num2.Current as
Microsoft.Office.InfoPath.Signature;
XPathNavigator sigNode = sig.SignatureBlockXmlNode;
sigNode.DeleteSelf();
}
}
}

But, though signature removed, infopath does not know about it until user
clicks Digital Signatures command or button.

How do I inform infopath, that signature removed or how to unsign form
correctly without user intervention.

Thank you!