Hi Nishath,
It is not compulsory for you to sell the house at Bambay if the property of chandigarh is a residential house property.
U/S 54 The asset must be a Long term Capital Asset means Should have been held by you for more than 36 months, on the date of Transfer.
If You want ot purchase a property in Delhi you have purchase it with in 2 years after the date of Transfer or if you have purchased any property 1 year before the transfer you can settle it off with the transfer.
If u have to construct a house then you can do it with 3 year.
The amount of Exemption will be
Cost of New Residential House including cost of land OR Capital Gain on the Transfer.
AND if you want to sell your property which is in bombay and want to invest the proceeds of both transfer in a Single property. You can do this it will be exempted U/S 54.
I hope you will find this information useful.
Regards
Vijay