To answer your question I have created a SIP calculator. Just enter the current value of your financial goal, which in this case is Rs. 5 lakhs, the expected rate of return which I have assumed as 12% per annum (I recommend to take a historical average, around 12-15%), the number of years you want to accumulate the amount in and the inflation rate which I have taken as 8% in this example. The inflation rate is important because it affects the future rate of your financial goal. So at 8% inflation a thing that costs Rs. 100 will cost Rs. 108 in a year from now.
As you can see you will need to invest Rs. 21, 407 in order to fund a vacation that costs Rs. 5 lakhs today.
Go ahead and download the SIP calculator. Happy investing.