Calculations with What If Parameters

[NMiller]

Pretty new to PowerBI and DAX. 

I currently have a calculated column that is calculating time to depth using assumed run speeds for the vertical section and lateral section of a well. The depths and lengths are 2 columns in my table. A team member requested that they be able to adjust the assumed speeds to see time savings by running in faster. 
I discovered what if parameters, which is exactly what I want, however columns evaluate at load time, not run-time. 

So, my question is, is there a way to convert a fairly simple calculation into a measure so I can make this happen?

Time_To_Depth = (depth/runSpeedA + length/runSpeedB)/60

[parry2k]

Time_To_Depth  as measure = 
var d = SUM(depth)
var speedA = SUM(runSpeedA)
var l = SUM(Length)
var speedB = SUM(runSpeedB)
var mycal = DIVIDE(d, runSpeedA, 0) + DIVIDE(l, runSpeedB, 0)
return  DIVIDE(myCal, [what if parameter name], 0)

try above, add it it as a measure.

[NMiller]

Forgot to mention that runspeed a and b would be the what if parameters. So I've got this in and its giving me pretty different results compared to my calculated colum with static values for the run speeds.

[parry2k · Accepted solution]

Time_To_Depth  as measure = 
var d = SUM(depth)
var l = SUM(Length)
var mycal = DIVIDE(d, [What if parameter for speed a], 0) + DIVIDE(l, [What if parameter for speed b], 0)
return  DIVIDE(myCal, 60, 0)

[NMiller]

Ok. Continuing on further, I am taking this theoretical value, and comparing it to an actual run time. Then trying to convert it to a percent off of the theoretical.  

Design Time Variance =
var tvd =averagea('Perf Data'[AVERAGE TVD])
var md = averagea('Perf Data'[Average MD])
var design = (divide(tvd,'Run In Speed - Vertical'[Run In Speed - Vertical Value],0)+DIVIDE(md-tvd,'Run In Speed - Lateral'[Run In Speed - Lateral Value],0)+DIVIDE(md,'Run Out Speed'[Run Out Speed Value]))/60
var actual = AVERAGE('Perf Data'[Wireline Duration])
var difference = actual-design
var percentage = DIVIDE(difference,design,0)
return percentage

When I return the difference var, the values match my calculated columns, but the percentages don't match. Any ideas why?