Adding total to a field based on another field in the same table

[TaiChi56]

Ok, i know that this should be easy but it is driving me crazy to figure out how to total one field every time another field has a number added. I have a field called MilesRan, this needs to be the field that keeps changing every time this field "CompletedMiles" changes. Each record will have the number of miles ran. I want the "MilesRan" field to total every time this happens. 

 

So if I have 5 records with the following number inputted:

5

10

6

4

3

9

8

 

So now "MilesRan" should show 45 miles when I get to record five. 

 

I have tried the following:

 

Sum (CompletedMiles)  "but I know that this is not takin into consideration that each record is getting a number"

 

Sum(CompletedMiles, MilesRan)  "This just doubles the outcome."

 

Thank you for any help. 

[LaRetta]

Try creating a summary field which would be Total Of 'Miles Ran'.

[comment]

Running. The summary field, not miles.

[TaiChi56]

You guys are awesome. I got it right away. Thank you very much for the help.