Formula for difference between numbers

[Lynngirl]

I need a formula to determine the difference between 4 numbers in a column, eg: 17,3,5,9.

The first row gives me the smallest number 3, the second row gives me the difference between the smallest number (3) and the next smallest number (5), the third row gives me the difference between the second smallest (5) and third smallest (9) numbers. The formula I need has to determine the difference between the third smallest (9) and the largest (17) numbers. The last row gives me the difference between the highest number and 23. If the value is 0 then it displays this -

The following formulas are what I used when I was working with 3 numbers in a column, now I need to change the formulas to work with 4 so some of these will need to change.

I have the formula for the first row =MIN(T3:T6)
the second row =IF(SMALL(T3:T6,2)-SMALL(T3:T6,1)=0,"-",SMALL(T3:T6,2)-SMALL(T3:T6,1))
the third row =IF(SMALL(T3:T6,3)-SMALL(T3:T6,2)=0,"-",SMALL(T3:T6,3)-SMALL(T3:T6,2))
fourth row ?
fifth row =SUM(23-T3)