How do I express this in DAX? (explicitly say when there is only total 1 row of data)

[JustinDoh1]

I am sharing my Pbix file here.

I am trying to set different output for case 1 & case 2.

case 1: for ClientID = 1 (John Doe):

Because this person only has Total only one row with Step=1 with Consent=Refused, output should be 0.

For the rest cases, like case 2 (Jane Doh) - if there is more than 1 total row beyond case 1: output should be default value of 1.

How can I explicitly say "if there is only one row of Step=1 & it's value has "Consent=Refused", output should be 0?

The measure is called "Step 1_0820".

I am guessing we might have to count the row(s) for row context first, and then look for the critiria? 

Currently, output for John Doe & Jane Doh are "", but somhow, total is 1.

When I tried with SUMX for this measure, output is more strange. 

Thank you so much for help.

[JustinDoh1]

@Greg_Deckler Thank you so much, Greg. Appreciated for help. It worked and I learned another grammar of DAX.

[Greg_Deckler · Accepted solution]

@JustinDoh1 Maybe:

Measure = 
  VAR __ClientID = MAX('Data'[ClientID])
  VAR __Table = FILTER(ALL('Data'),[ClientID]=__ClientID && [Step]=1)
  VAR __Count = COUNTROWS(__Table)
  VAR __Refused = COUNTROWS(FILTER(__Table,[Consent]="Refused"))
RETURN
  IF(__Count = 1 && __Refused = 1,0,1)