<obout:OboutTextBox runat="server" ID="OboutTextBox1" MaxLength="4"> <ClientSideEvents OnKeyPress="TextBox_KeyPress" OnKeyUp="TextBox_KeyPress"/></obout:OboutTextBox><obout:OboutTextBox runat="server" ID="OboutTextBox2" MaxLength="4"> <ClientSideEvents OnKeyPress="TextBox_KeyPress" OnKeyUp="TextBox_KeyPress" /></obout:OboutTextBox><obout:OboutTextBox runat="server" ID="OboutTextBox3" MaxLength="4"> <ClientSideEvents OnKeyPress="TextBox_KeyPress" OnKeyUp="TextBox_KeyPress" /></obout:OboutTextBox><obout:OboutTextBox runat="server" ID="OboutTextBox4" MaxLength="4"> <ClientSideEvents OnKeyPress="TextBox_KeyPress" OnKeyUp="TextBox_KeyPress" /></obout:OboutTextBox>
function TextBox_KeyPress(sender, key) { var index = parseInt(sender.ID.replace('OboutTextBox', '')); if (sender.value().length == 4 && index < 4) { var nextTextBox = eval('OboutTextBox' + (index + 1)); if (nextTextBox) { nextTextBox.focus(); } }}