DateDiff between different stages

Hi, 

I finally find a way to do it I think there is others way to simplify the formula but it's working.  

Many thanks for your contribution.  

Days Challenge = 
IF (
    'Opportunity Field History'[OldValue] = "Challenge";
    DATEDIFF (
        CALCULATE (
            MIN ( 'Opportunity Field History'[CreatedDate] );
            ALLEXCEPT (
                'Opportunity Field History';
                'Opportunity Field History'[OpportunityId]
            );
            'Opportunity Field History'[Field] = "created"
        );
        'Opportunity Field History'[CreatedDate];
        DAY
    );
    IF (
        'Opportunity Field History'[OldValue] = "Closing";
        DATEDIFF (
            CALCULATE (
                MIN ( 'Opportunity Field History'[CreatedDate] );
                ALLEXCEPT (
                    'Opportunity Field History';
                    'Opportunity Field History'[OpportunityId]
                );
                'Opportunity Field History'[NewValue] = "Closing"
            );
            'Opportunity Field History'[CreatedDate];
            DAY
        );
        IF (
            'Opportunity Field History'[OldValue] = "Solution";
            DATEDIFF (
                CALCULATE (
                    MIN ( 'Opportunity Field History'[CreatedDate] );
                    ALLEXCEPT (
                        'Opportunity Field History';
                        'Opportunity Field History'[OpportunityId]
                    );
                    'Opportunity Field History'[NewValue] = "Solution"
                );
                'Opportunity Field History'[CreatedDate];
                DAY
            );
            IF (
                'Opportunity Field History'[OldValue] = "Value";
                DATEDIFF (
                    CALCULATE (
                        MIN ( 'Opportunity Field History'[CreatedDate] );
                        ALLEXCEPT (
                            'Opportunity Field History';
                            'Opportunity Field History'[OpportunityId]
                        );
                        'Opportunity Field History'[NewValue] = "Value"
                    );
                    'Opportunity Field History'[CreatedDate];
                    DAY
                );
                BLANK ()
            )
        )
    )
)