If you're needing something developed, I strongly recommend hiring a developer. Or getting yourself sent on an ABAP course... or buying an ABAP book and learning it yourself.
However, I'm fairly sure that there are existing reports that give you this information - try ST13, BW-TOOLS, process chain analysis.
Or RSPC, look at a chain log and choose "Runtime Statistics".
Rather than write a bespoke program, another route would be to create a datasource on RSPCPROCESSLOG and load the data into a cube or DSO. Then you can run queries on it.