What speed Celeron?
The slowest Celeron, the 266 without cache, was equivalent in performance to a Pentium MMX 233MHz.
As for current Celerons, the slowest of the Pentium 4 class at 1.7GHz gives performance similar to the Pentium III 1.2GHz in Office Applications. However, the Pentium 4 based Celerons have mixed performance across a range of applications, so you should check if it suits your needs. You will run into quite a few problems trying to run Windows 95 on one of these systems though.