VINTAGE function and attribute over time

Hi,
I would like the FIXOM and VAROM to change after a certain time after the actual investment year for a certain process. Is it possible to use the Vintage-function to make the attribute change after a certain time after the investment is taken, rather than for a certain year? E.g. 20 year after the actual investment year FIXOM is increased with 30 % and not specfically in year 2XXX.

Can anyone give an example how I could implement this in a proper way? It would be very helpful.

Thank You!!!

I didn't find the right solution from the Internet.
References
http://forum.kanors-emr.org/showthread.php?tid=457
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