I need to create probably some kind of pivot or lookup table, neither of which I've done in a long time. I'm having a hard time thinking about what function I actually need to use to do this.

The calculation is regarding a kind of linear process. The process has 12 main parts, each divided into 10 decimal sub-parts, 0.0, 0.1, 0.2, etc., up to 12.0. So it's actually 120 discrete sub-parts. If doing the complete process, it would start at 0.0 and proceed through each sub-part until it reaches 12.0. But that never happens. Each instance of the process has its own starting point, i.e., it may start in the middle, as in halfway through part 3.3, which I would represent as 3.35. The process doesn't jump around -- once started, it finishes the part that it's on and proceeds to the next higher level. In this case it would go straight to 3.4 and start on that.

Each sub-part takes a particular amount of time to complete. So I have a table with columns indicating A) the decimal sub-part in question; B) the number of hours required to complete that sub-part; and C), by calculation, the advancement in completing the decimal sub-part per hour invested (=the inverse of col. B).

So using the inputs of:

--The starting point for this instance

--How many hours the process has been running

I need the calculated answer of what sub-part this instance should be working on at the moment.

So, it started at sub-part 3.35 and ran for 10 hours. Sub-part 3.3 takes 2 hours, so this instance needs 1 hour to finish it as it's started in the middle of the sub-part. Sub-part 3.4 takes 4 hours, so that gets finished, we've spent 5h so far. Subpart 3.5 also takes 4h; it gets finished too, using 9h so far. Subpart 3.6 takes 2h, in 10h total it can do the first half of this level and finishes at level 3.65. That's the answer that I want it to return, 3.65. Input starting point 3.35 and hours 10, it makes the appropriate calculation from my tables and returns back 3.65

Guidance appreciated