How to sort the X axis in Chart?

Hi, everyone,

I, design a chart using formula. like below.

@CombinePeridAndDate is a formula.

totext({DataTable_SHUIPING.周期},0) & "(" & totext(Date({DataTable_SHUIPING.日期})) & ")"

Now the chart shows

Because the "Order" is "A", I want it show A, using the number before"(".

Which means, 10(2013/1/12) is at the last position.

How to set the orders?

Thanks.