// ComplexBorderSide 설정
FarPoint.Win.ComplexBorderSide bottomborder = new FarPoint.Win.ComplexBorderSide(true, Color.Gray, 1, System.Drawing.Drawing2D.DashStyle.Solid, null, new Single[] { 0f, 0.33f, 0.66f, 1f });
FarPoint.Win.ComplexBorder complexborder = new FarPoint.Win.ComplexBorder(null, null, null, bottomborder);
for (int i = 0; i < fpSpread1.Sheets[0].RowCount - 1; i++)
{
    if (fpSpread1.Sheets[0].Cells[i, 1].Text != fpSpread1.Sheets[0].Cells[i + 1, 1].Text)
    {
        // 조건에 부합하는 셀의 Border 설정
        fpSpread1.Sheets[0].Cells[i, 0, i, fpSpread1.Sheets[0].ColumnCount - 1].Border = complexborder;
    }
}