I didn't really know where else to pose this question, but...
Let's say you've got
So if you have 5000, you'd use 38. If you had 10000, you'd use 29.
Now I have a table of these pairs, in ascending order on amt for every 5000. (ie. 5000, 10000, 15000, 20000, ....).
The problem I'm facing is that if I have, say, 6000, I don't have a matching 'inc'. Now I can't use 38, or 29, but I have to use something in between. But that something has to be proportionate if 'amt' is 5500 or 8900.
I hope that makes sense so far.
Now I think this has something to do with numerical analysis, but I really just can't remember what or how to do this!
If anyone can help, I'd really appreciate it. If you require more information, just ask.