Available Hours based on Start and End Dates

Hi Everyone :smileyhappy:

I am trying to calculate available hours for the month for each employee where their available hours would be adjusted based off their Start and End Dates:

Example: Start Date: 15 July 2019 = his/her available hours for that month only would be 104 based off a column in my Date table that calculates the available hours for each day.

Example End Date: 22 July 2019 = Summing available hours from the start of the End Date till the end of the End Date.

I tried to create a measure but does not return the correct result:

Available Hours = 

VAR Start_Date = MAX ( Staff[Date Employed] )
VAR End_Date = MAX ( Staff[Staff_Termination_Date] )

VAR Start_Date_YM = FORMAT ( MAX( Staff[Date Employed]) , "YYYYMM")
VAR End_Date_YM = FORMAT( MAX(Staff[Staff_Termination_Date]) , "YYYYMM")

VAR Avail_Hours = CALCULATE( SUM(Dim_Date[Available Hours]) , Dim_Date[YYYYMM] )

VAR Dim_Date_YM = FORMAT(MAX(Dim_Date[Calendar_Date]) , "YYYYMM")

VAR Result1 =
SWITCH( TRUE() , 
Start_Date_YM = Dim_Date_YM , CALCULATE ( Avail_Hours , DATESBETWEEN ( Staff[Date Employed] ,  MAX( Staff[Date Employed] ) ,  EOMONTH ( Start_Date , 0) ) ) ,
End_Date_YM = Dim_Date_YM , CALCULATE ( Avail_Hours , DATESBETWEEN ( Staff[Staff_Termination_Date] , STARTOFMONTH (  Staff[Staff_Termination_Date] ) , MAX( Staff[Staff_Termination_Date] ) ) ) ,
Avail_Hours )

RETURN

Result1

Your help is much appreciated.