Combine multiple if statements and be able to add priority

Hi All,

I'am creating a new column in which I want to be able to determine if a project is active.

A project is active when:

Startdate is <= today and when the enddate is >= today. But sometimes the enddate is not filled.

If that is the case, the formula must look at a second value (End_Date_PO_Sub_agreement), when the second value is not filled the formula has to check a third value (Expected_Project_End_Date). 

In some cases all the values are filled and then the priority must be the enddate.

Active projects = IF(Placement[cxsrec__Start_date__c] <= TODAY() && Placement[cxsrec__End_date__c] >= TODAY(); "active" ; 
    IF(Placement[cxsrec__Start_date__c] <= TODAY() && Placement[Expected_Project_End_Date_TMC__c] >= TODAY(); "active" ; 
        IF(Placement[cxsrec__Start_date__c] <= TODAY() && Placement[End_Date_PO_Sub_agreement__c] >= TODAY(); "active" ; BLANK())))

Any ideas would be much appericated.  Thanks for any and all help in advance!