Dates And Tick Boxes In A Form

Hey,

I hope this is the right place to be posting this...

I've set up a database about unemployed people and it has a field called "Start Date of Employment", where a date is manually entered by the user.

Further down, there are two tick boxes - one called "13 weeks", and one called "26 weeks".

Now, what I'd like to happen, is that the database looks at the "Start Date of Employment", and then if 13 weeks have passed, it puts a tick in the 13 weeks box. Then when 26 weeks have passed, it puts a tick in that box also.

I'm assuming that this is possible, but I have no idea how.

Can anybody help?

Thanks

Dan