DAX power pivot count Items matching in two tables

[dicken]

hi,

I'd like to write a measure to count the items in TableB that are in TableA, to do this I've got as far as

CountMatchingM :=
VAR CountT1 =
    COUNTROWS ( Table1 )
VAR Table2Items =
    DISTINCT ( Table2[ItemTwo] )
VAR anser1 =
    CALCULATE ( CountT1, FILTER ( ALL ( Table1 ), Table1[Items] = Table2Items ) )
RETURN
    anser1

The problem is I get an extra row for all non-matching items, I thought using DISTINCT rather than VALUES might fix this, but it hasn't.
Suggestions please also if there are better ways of achieving this let me know.

Richard.