here is the solution for your query. try it now.
Select SUM(TDays) SumDays
From (
Select Id, Status, UserId,
Case When (Status = 'Inactive') Then 0 Else
(DATEDIFF(DAY,StatusDate,(Case When (NextDate IS NULL) Then GetDate() Else NextDate End)))
End TDays
From (
Select Id, Status, UserId, Case When (ProgramStartDate IS NOT NULL) Then ProgramStartDate Else StatusDate End StatusDate,
(Select Min(StatusDate) From StatusMast M Where M.StatusDate > S.StatusDate) NextDate
From StatusMast S
) As Stat
)As TotDay
Your output is :
SumDays
25