partial result as percentage of total

[alca1]

Let's say I have this data table:

{id_order, date_order}

I want to show the n. of orders in a period as percentage of the total number of orders.

I defined id_order as a countAll measure and date_order as dimension.

I used date_order as row and id_order as columns in crosstab report.

Next I added a filter on date_order: is between.

What I would like to show is just a box, with inside a BIG number with the percentage of orders against the total and below the period.

I tried to introduce a calculated measure PercentageOf ("id_order","Total") but it just works per row. (and even so number are not right)

I'm a bit lost, I don't how to do it nor I find relevant resources/examples