diff --git a/EduNetworkBuilder/IPAddressEntry.Designer.cs b/EduNetworkBuilder/IPAddressEntry.Designer.cs
index 8bd79a6..fd16518 100644
--- a/EduNetworkBuilder/IPAddressEntry.Designer.cs
+++ b/EduNetworkBuilder/IPAddressEntry.Designer.cs
@@ -103,6 +103,7 @@
             this.btnCancel.Text = "Cancel";
             this.btnCancel.UseVisualStyleBackColor = true;
             this.btnCancel.Click += new System.EventHandler(this.btnCancel_Click);
+            this.btnCancel.CausesValidation = false;
             // 
             // btnOK
             // 
diff --git a/EduNetworkBuilder/IPAddressEntry.cs b/EduNetworkBuilder/IPAddressEntry.cs
index 6c50d24..a9100cb 100644
--- a/EduNetworkBuilder/IPAddressEntry.cs
+++ b/EduNetworkBuilder/IPAddressEntry.cs
@@ -194,6 +194,8 @@ namespace EduNetworkBuilder
 
         private void tbGateway_Validating(object sender, CancelEventArgs e)
         {
+            if (!WellDone) return;
+
             Network mynet = NB.GetNetwork();
             if (ParentDevice != null)
             {
@@ -221,6 +223,8 @@ namespace EduNetworkBuilder
 
         private void tbNetmask_Validating(object sender, CancelEventArgs e)
         {
+            if (!WellDone) return;
+
             UInt32 taddress = tbNetmask.Text.ParseIp();
             tbNetmask.Text = taddress.ToIpString();
             if (DHCPInterface != null)
@@ -236,6 +240,8 @@ namespace EduNetworkBuilder
 
         private void tbIPAddress_Validating(object sender, CancelEventArgs e)
         {
+            if (!WellDone) return;
+
             UInt32 taddress;
             Network mynet = NB.GetNetwork();
             NB_IPAddress tIPAddress = null;