Bar chart Expression

[#1]

Hi guys,

I have a bar chart where dimensions : (snapshotdate,salesstage) , expression : sum(amount)

image is attached below....

now i want my bar chart to show the next 90 days amount for every snapshotdate....

i am trying to use following logic but not getting proper results....

if(floor(closingdate)>=floor(today()) and  num(floor(closingdate))-num(floor(today()))<=90,closingdate)

how to integrate above logic in bar chart expression to get amount....