Field selection with set expression in toggle button

[anseglko]

I'm using the button for navigation extension and I want to toggle one field value. The idea is to select all the values below one limit. The limit is simply

avg(field1)+2*stdev(field1)

I found out that 

= '<= $(=92870)'

 works perfectly, but when I try to replace number with the limit like this

='<= $(=$(=avg(field1)+2*stdev(field1)))'

the button stops working, even when the expression editor says everything is OK and even shows the correct limit exactly as when I wrote the number manually

 

Any idea why this doesn't work? 

[anseglko · Accepted solution]

Solved it myself. The number had to be rounded to a full integer for the button to work.. 

='<= $(=round(avg(field1)+2*stdev(field1)))'