|is there a way to have an ms spreadsheet calculate due dates for me instead of me inputting them manually.|
The simple answer is yes.
On way, is if you have a date in cell A1
and you wish to add 60 days then a simple:
will return a date, 60 days from now.
There are approximately 20 different commands in Excel that deal with Dates & Time so, if you need help, you will have to be a bit more specific in your explanation.
An example of your worksheet, with Column Letters and Row Numbers would be helpful.
See this How-To, which explains the use of the PRE tags in posting your data.