UDV Syntax Issue

Question

Hello Experts,
The following UDV code works until I add the WHERE clause, at which time I get a syntax error near keyword WHERE:
DECLARE @x INTEGER
SET @x = $[$3.2.NUMBER] WHERE $[$3.1.0] = 'Mileage'
SELECT CASE
WHEN @x BETWEEN 1 AND 19 THEN 10
WHEN @x BETWEEN 20 AND 39 THEN 20
WHEN @x > 39 THEN 30
END
(This is basically retrieving a value from column 2 of a matrix where column 1 has a value of 'Mileage'.)
SELECT $[$3.2.NUMBER] WHERE $[$3.1.0] = 'Mileage' works as a separate query, but I cannot get that functionality into my above code.
Regards

Answer 1

Solved, just needed to bracket it into a subquery.. could have sworn I tried that...
SET @x = (SELECT $[$3.2.NUMBER] WHERE $[$3.1.0] = 'Mileage')