Filter tabel by same values in different rows

[icturion]

Can someone help me with a formula for a calculated column that makes it possible to show only records that have two items A and B within the same number?

Example data:

NR	Item
1	A
1	B
2	A
3	A
3	B
4	A
5	A
5	C

THe result i'm looking for is:

NR	Item
1	A
1	B
3	A
3	B

[ppm1 · Accepted solution]

Here's a column expression that returns T/F for Numbers 1 and 3 rows.

ABonly =
VAR items =
    CALCULATETABLE ( DISTINCT ( T1[Item] ), ALLEXCEPT ( T1, T1[NR] ) )
VAR AB = { "A", "B" }
RETURN
    COUNTROWS ( INTERSECT ( items, AB ) ) = 2
        && COUNTROWS ( items ) = 2

Pat