Conversion of PC Based app to Web

I have an MS Access app (front end/back end) that is data entry/number crunching/extensive reporting app that we license to our users.
I have been told to get it on the web for all our users.
I need some guidance as to what language(s) I need to learn to get this job done.
I have expertise knowledge in MS Office/VB/Pascal/PowerBuilder/Crystal Reports/SQL (but no web experience).
As a kicker, they also want it to be portable for the user (app and data local – no internet connection) and be able to sync the data.
Any guidance would be greatly appreciated.