Select records inbetween

Hello,

I would like to know if there is an easy way to select records between a certain data

For exemple I have a table that looks a bit like this :

I would like to select records only between Jan and Net, or better between the ------------ 

Reason is that I need to transform those numbers and round them to 2 decimals, without touching to the others variables.

I know the easy would be to put a record ID and then select with the > or = from the filter tool.

But I can't rely on record position (as I'm used to), as I have to make my workflow the most dynamic possible and the position of my records is likely to change with other data set.

If anyone has a formula, or a way around to solve this, 

Thanks!