We have 3 fields  Ex_Period_End_Date__c (DataType Date) and Contract_Notice_Exclusivity_months__c (DataType Number), Exclusivity_Date__c (Formula field).

Our requirment is Exclusivity_Date__c = Ex_Period_End_Date__c - Contract_Notice_Exclusivity_months__c

By using formula feild i wrote below code, it works for addition i.e, Ex_Period_End_Date__c + Contract_Notice_Exclusivity_months__c

if(AND( NOT( ISBLANK(Ex_Period_End_Date__c) ),NOT( ISBLANK(Contract_Notice_Exclusivity_months__c ) )),DATE ( 

/*YEAR*/ 
YEAR ( Ex_Period_End_Date__c ) + FLOOR ( (MONTH ( Ex_Period_End_Date__c ) + Contract_Notice_Exclusivity_months__c - 1)/12), 

/*MONTH*/ 
CASE ( MOD ( MONTH ( Ex_Period_End_Date__c )+Contract_Notice_Exclusivity_months__c, 12 ),0,12,MOD ( MONTH ( Ex_Period_End_Date__c )+Contract_Notice_Exclusivity_months__c, 12 )), 

/*DAY*/ 
MIN ( DAY ( Ex_Period_End_Date__c ), 
CASE ( MOD ( MONTH ( Ex_Period_End_Date__c )+Contract_Notice_Exclusivity_months__c,12 ) ,9,30,4,30,6,30,11,30,2, 

/* return max days for February dependent on if end date is leap year */ IF ( MOD ( YEAR ( Ex_Period_End_Date__c ) + FLOOR ( (MONTH ( Ex_Period_End_Date__c ) + Contract_Notice_Exclusivity_months__c)/12) , 400 ) = 0 || ( MOD ( YEAR ( Ex_Period_End_Date__c ) + FLOOR ( (MONTH ( Ex_Period_End_Date__c ) + Contract_Notice_Exclusivity_months__c)/12) , 4 ) = 0 && MOD ( YEAR ( Ex_Period_End_Date__c ) + FLOOR ( (MONTH ( Ex_Period_End_Date__c ) + Contract_Notice_Exclusivity_months__c)/12) , 100 ) <> 0 
) 
, 29,28) 

,31 ) ))-1, 

null)

The above snippet works for addition but our logic changed to substraction, can any one help out



Regards,
Rahul