DataGrid单元格数据输入格式检测方法

public int nPreX = -1;//初始化位置变量Ｘ
public int nPreY = -1;//初始化位置变量Ｙ
private bool bChangeCell = true;//标志位

private void DataGrid_CurrentCellChanged(object sender, System.EventArgs e)
{
if (bChangeCell ==true)
{
if(nPreX!=this.CurrentCell.RowNumber||nPreY!=this.CurrentCell.ColumnNumber)
{
if( nPreX==-1 && nPreY==-1 )
{
nPreX = this.CurrentCell.RowNumber;
nPreY = this.CurrentCell.ColumnNumber;
return;
}

if(this[nPreX,nPreY].ToString().Length < 5)
{
MessageBox.Show("Error");
bChangeCell = false;
this.CurrentCell = new DataGridCell(nPreX,nPreY);
return;
}
else
{
nPreX = this.CurrentCell.RowNumber;
nPreY = this.CurrentCell.ColumnNumber;
}
}
}
else
bChangeCell =true;
}