Create a calculation
if Year(Admit Datetime) < parameter then [Number of Records] end
and in your original calculation, replace [Number of Records] with this new calc
That works but I have to calculate the thresholds on percentages as well as age groups:
What can I do if I need to show the following thresholds in one calculation?
IF SUM([Number of Records]) >70 only for Admit age under 35 years THEN 'LOW'
ELSEIF SUM([Number of Records]) >25 AND SUM([Number of Records]) <70 only for Admit age under 50 years THEN 'MID'
ELSEIF SUM([Number of Records]) <25 only for Admit age under 50 years THEN 'HIGH'
Then you would need 2 calculations in the same format I did and replace parameter with 35 in one case and 50 in the other.
And if you want the user to be able to select the ages then you need two different parameter.