You can try to use the OnBeforeAdd client side event of WebGrid. It is the client side (JavaScript) function that will be invoked before new row request is invoked.

In this event, you can check whether column NAME or EMAIL is set or not. If they are set, call the SetText and SetValue method to STATUS column.

Example:

function WebGrid1_OnBeforeAdd(controlId, tblName, rowObject)
{
    var WebGrid1 = ISGetObject("WebGrid1");
    var NameCell = rowObject.Cells.GetNamedItem("Name");
    var EmailCell = rowObject.Cells.GetNamedItem("Email");
    var StatusCell = rowObject.Cells.GetNamedItem("StatusCell");
    if (NameCell.Value != "" && EmailCell.Value != "")
    {
        StatusCell.SetText("Internal");
        StatusCell.SetValue("1");
    }
    else
    {
        StatusCell.SetText("External");
        StatusCell.SetValue("2");
    }
            
    return true;
}

Hope this helps.

thank you but i must check if the value that i entered in the webcombo exists in the datasource. 

when i enter a value it autocomplete it and the status is internal, but when i enter a value that is not in the datasource the status should change to external before adding. 

In my opinion, we need to enable AllowAddItem property of WebCombo and assign a JS function for the OnAddItem client side event. This event fired when an item is about to be added.

You may try to set the text to external in this JS function before the return true line. Please feel free to let me know whether this helps or not.