Using named cells:

Manfg_Date: [any date]
Ref_Date: 1-Jan-91
Interval: =IF(Manfg_Date<Ref_Date,3,5)
Last_Hydro: [any date]
Next_Hydro: =Date(Year(Last_Hydro)+Interval, Month(Last_Hydro),
Day(Last_Hydro))



"Chris" wrote in message
...
I have on cell that has an original manfg. date 1/1/90 (this date will
change) the next hydro date is either 3 or 5 years depending on the date.
prior to 1/1/91 cylinder must be done every three years and after 1/1/91
they
must be done every 5 years. I am stuck on the formula asd I have it now
=IF($D$3<B16,1095+D3,1825+D3) any assitance would be of great help.
Thnaks