Dividing sum result in multiple cells

Question

I'm new to all this and i hope you can help me, i have some knowledge inbut I'm stuck with this. my problem is that i don't know to divide sum result in multiple cells. my problem looks something like this if sum of parts is 5000 then first 500 part costs..., second 2000 costs... and rest costs...

Answer

I assume that it's always first 500, next 2000 etc

=if(SumOfparts>500,500*cost,SumOfParts*cost)

would give you first part

=if(SumOfparts>2500,2000*cost,(SumOfParts-500)*cost)

would give you second - and hopefully would give you the idea of how to carry on the formula.