Just write some if statements. First off, make sure that you have a 4 digit task number
if the length of the tasknumber = 4 then
if date = today's date then
go to the corresponding link
elseif date = today's date + 1 day then
go to the tomorrow date link
elseif date = today's date - 1 day then
go to the yesterday date link
else
have a message stating that the date is incorrect or does not have a corresponding link
end if
Hope that this pseudocode helps