I need to subtract Time From same column by applying filters on it

Question

I have [scan Time] column and [Location] column which have different locations like Security T2, Post security T2 DOM , Post Security T2 INT.

So want to subtract Scan Time of Post security T2 DOM and Security T2 also Post security T2 INT and Security T2

So i have tried to make measure like this

Post_Security_T2_DOM - Security_T2 = var Security_T2 = CALCULATE(AVERAGEX( FILTER(EGateData, EGateData[Location] = "Security-T2"), (EGateData[Scan_Time])))

var Post_Security_T2_DOM = CALCULATE(AVERAGEX( FILTER(EGateData, EGateData[Location] = "Post Security T2 DOM"), (EGateData[Scan_Time])))

var Total_Time = CALCULATE(Post_Security_T2_DOM - Security_T2)

return FORMAT(Total_Time,"HH:MM:SS")