Count number of unique items in column that meet some criteria

[#1]

Suppose in "Big Class" I'd like a formula that counts the number of unique names of people at or less than the height of the person in the current row.  How can I do that?

I have this:

thisHeight = :height;
Col N Unique( :name, :height <= thisHeight );

I realize the second parameter is the grouping parameter, and it's more intuitive to try to constrain what gets passed into the first parameter, but I haven't had any luck with anything I've tried to this point.

[#2]

Here's a technique for exploring the rabbit hole:

New Table( "Untitled",
	Add Rows( 3 ),
	New Column( "a",
		Formula(Write( "\!nA" || Char( Row() ) );Row();),
		Set Selected
	),
	New Column( "b",
		Formula(Write( "\!nB" || Char( Row() ) );:c + :d + 100;)
	),
	New Column( "c",
		Formula(Write( "\!nC" || Char( Row() ) );:a + 1000;)
	),
	New Column( "d",
		Formula(Write( "\!nD" || Char( Row() ) );:a + 10000;)
	),
	new column( "e",
		formula(write("\!nE" || char(row())); asconstant(write("\!nE as constant "|| char(row())); Q=a+b+c+d); Q;)
	)
);

/*

A1 << A must be done first, every other column depends on A
A2
A3
D1
D2
D3
C1
C2
C3
B1 << B must be after C and D
B2
B3
E as constant 1 << the constant is calculated before the first cell, but using row 1
E1 << E must be last; the asconstant value uses all other columns
E2
E3

*/

The ; is a JSL operator that executes a series of statements and returns the last statement's value. That means a print/show/write statement can be prepended to a calculation to make a trace in the log.

Above I learned the asconstant(...) is pulled out before the first row is calculated, but with row 1 as the current row. 

JMP also sorts through the columns to figure out which ones can evaluate first.

[#3]

Column E would make more sense like this:

	New Column( "e",
		formula( 
			Write( "\!nE" || Char( Row() ) ); 
			As Constant( Write( "\!nE as constant " || Char( Row() ) ); a + b + c + d; ); 
		)
	)

The Q variable is not needed and hides AsColumn's purpose in life.