Multiple Conditions for calculating weeks between 2 dates

I am creating a waiting list calculation with the following headings;

I was the formula to calculate the date between referred and activated but with the following conditions;

1 - If C2 is empty calculate from todays date (TODAY()-A2)/7

2 - If C2 is populated calculate from that date (C2-A2)/7)

3 - If A2 is blank return a blank cell IF(ISBLANK(D2),"",

I've came up with the following formula but can't get it to work for me; 

=AND(IF(ISBLANK(C2),((TODAY()-A2)/7),((C2-A2)/7)),(IF(ISBLANK(A2),"",(TODAY()-A2)/7)))

I am working off Excel 2016.