how to get max min date from a tuple

suppose i have a bunch of people (with dimension) they have a bunch of claims (dimension)

and in each claim there is a bunch of records with amount and date!

those records/transactions form a cube with measures like amounts paid

Ultimately i need to get the average time between first and last payments (claim trail length)

for each person (adjuster)

but I cannot even get to extract the first (min) and last (max) transaction date for each person/claim set

with member LastDate as

!!!!! max date with the highest key perhaps???

but need to get inside tupe of person/claim

SELECT

{MEASURES.[LastDate]}

ON 0,

     ([Person].[Hierarchy].[Person Name].members, 

	 [Claims].[ID].members),

ON 1

FROM [mycube]

Thanks!!!!