Preventive Schedule Automatic Plan Visit

Dear Team

I am working on an Preventive maintenance schedule excel sheet,In which i would like to highlight Planned visit month based on Following par-maters 1)Start & End date of Contract
2) No of visits to be done(Like Quarterly,Bimonthly,Monthly etc)
3)Rest off cells should be white and planned visit should be highlighted

Take an example for one of job we have contract start date:April 15 2015 & contract end date April 14 2016 with frequency Quarterly so the first visit should be in April month then accordingly in 12 months based on frequency i.e Quarterly next visit should be august,then december and then april of next year.

Attached sheet for reference