Capital gain tax implication

Q: Dear Sir,I sold a residential property X and gained sales proceed Y. I invested the proceed Y in another residential property Z.If I wish to sell this Property Z before 3 years then I understand that I have to pay the short term capital gain tax. Is that right ?My question is whether I will be taxed only for the difference amount (Selling price – Purchased price) or will I be taxed for the whole sale proceed that I get from selling property Z.Can I reinvest the sale proceed that I get from selling property Z into another residential property to avoid capital gain tax.I am very confused, kindly help.Thanks & RegardsRaghu