I have three table :

Table one 【member data】

which have

{start date}

{end date}

{single linked to weekly summary}

table two【activities】

{date of activities}

{multiple linked to weekly summary per person}

table three 【weekly summary per person】

{week number}

{single linked to member data}

{multiple linked to activities}

If I want each activity to have the accurate number of member during {date of activity} , to get the real attendance rate.

How could I do to set up the formula…??