次のコードは、TextBoxCellで入力可能文字数を6バイトに設定する例です。

[Visual Basic]

Imports System.Text
Imports GrapeCity.Win.MultiRow

Private Sub GcMultiRow1_EditingControlShowing(ByVal sender As System.Object, ByVal e As EditingControlShowingEventArgs) Handles GcMultiRow1.EditingControlShowing
　　If TypeOf e.Control Is TextBoxEditingControl Then
　　　　Dim textBox As TextBoxEditingControl = TryCast(e.Control, TextBoxEditingControl)
　　　　If textBox IsNot Nothing Then
　　　　　　RemoveHandler textBox.TextChanged, AddressOf Me.textBox_TextChanged
　　　　　　AddHandler textBox.TextChanged, AddressOf Me.textBox_TextChanged
　　　　End If
　　End If
End Sub

Private Sub textBox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs)
　　Dim textBox As TextBox = TryCast(sender, TextBox)
　　Dim sjis As Encoding = Encoding.GetEncoding("Shift-JIS")
　　Dim maxLengthAsByte As Integer = 6
　　Dim sourceText() As Byte = sjis.GetBytes(textBox.Text.ToCharArray())

　　If sourceText.Length > maxLengthAsByte Then
　　　　Array.Resize(Of Byte)(sourceText, maxLengthAsByte)
　　　　textBox.Text = sjis.GetString(sourceText)
　　　　textBox.SelectionStart = textBox.Text.Length
　　End If
End Sub

[C#]

using GrapeCity.Win.MultiRow;

private void gcMultiRow1_EditingControlShowing(object sender, EditingControlShowingEventArgs e)
{
　　if (e.Control is TextBoxEditingControl)
　　{
　　　　TextBoxEditingControl textBox = e.Control as TextBoxEditingControl;
　　　　if (textBox != null)
　　　　{
　　　　　　textBox.TextChanged -= new EventHandler(textBox_TextChanged);
　　　　　　textBox.TextChanged += new EventHandler(textBox_TextChanged);
　　　　}
　　}
}

private void textBox_TextChanged(object sender, EventArgs e)
{
　　TextBox textBox = sender as TextBox;
　　Encoding sjis = Encoding.GetEncoding("Shift-JIS");
　　int maxLengthAsByte = 6;
　　byte[] sourceText = sjis.GetBytes(textBox.Text.ToCharArray());

　　if (sourceText.Length > maxLengthAsByte)
　　{
　　　　Array.Resize<byte>(ref sourceText, maxLengthAsByte);
　　　　textBox.Text = sjis.GetString(sourceText);
　　　　textBox.SelectionStart = textBox.Text.Length;
　　}
}

参考:

• InputManCellのGcTextBoxCellを使用すると、バイト単位で入力文字数を簡単に指定できます。(GcTextBoxCell.MaxLengthUnitプロパティ)