Sorry for multiple edits, I forgot angle brackets get eaten sometimes by the inline code tags so I converted one to an ugly code block.
One way would be to use Regex to create a tiny bit of structure. If I'm reading this right, at the moment your problem is that though you may have fields named "counter" and "value", you can't actually correlate which counter goes with which value. So, let's create a few variables.
I'll show you a sort of brute force way because it's more clear. Don't be scared by the rex, I'll explain in a bit.
...my search that returns the above events... | rex field=_raw "(?m)Drive\s+C:\s+Value\s+=\s+(?<c_drive>[^ ]+)"
The string for the rex says...
(?m) - search across multiple lines
Drive - find the exact string Drive
\s+ - followed by one or more spaces or other whitespace characters
C:\s+Value\s+=\s+ More strings and spaces in a certain order
(?...) These indicate I'm creating a new field out of the next things I specify
<c_drive> ( Name whatever I find as the fieldname c_drive)
[^ ]+ The plus says to match one or more of the items inside the brackets, EXCEPT the first character inside the bracket is ^ which means NOT. So what it's actually saying is to match one or more non-space characters, so it'll then grab 49.49 or whatever up to the next space.
You can repeat the entire thing changing a few small variables and create a second rex for d_drive.
...my search that returns the above events...
| rex field=_raw "(?m)Drive\s+C:\s+Value\s+=\s+(?<c_drive>[^ ]+)"
| rex field=_raw "(?m)Drive\s+D:\s+Value\s+=\s+(?<d_drive>[^ ]+)"
