Window aggregate UDFs can take literals, literal expressions, column names (sales, for example), or column expressions (sales + profit) as arguments.
Window aggregates can also take regular aggregates as input parameters to the PARTITION BY and ORDER BY clauses. The RESET WHEN clause can take an aggregate as part of the RESET WHEN condition clause.
The rules that apply to the arguments of the window aggregate UDF are the same as those that apply to aggregate UDF arguments, see Aggregate UDF.