There could be two ways of solving this.
1) Add a computed column (SQL) before the aggregations happen. This would look something like
CASE WHEN pageurl like '%order%' THEN 1 ELSE 0 END
Give this column a name, then use the aggregation functions in the next section to use SUM
2) Use custom aggregates wrapping the computed column and aggregate in one go:
SUM(CASE WHEN pageurl like '%order%' THEN 1 ELSE 0 END)
Hope this helps!