How to move data in a different row to the first row by creating a new column?

[Emmm]

Dear helpers, really need your help on this! 

Please see attached for my input, I'm trying to create a new column (see result excel) called "new time". New time's data should = transactiondatetime for the same "businessdate", under the same "CODE", under the same "checknumber", under the same "menuitemnumber", when the "FLAG"=1. 

If there are more than two rows for the same item under the same CODE/checknumber/menuitemnumber, the "New time" should have data for the earliest transactiondatetime row, and leave it as empty for the later ones. 

I also need to calculate the date time difference between new time and transactiondatetime. 

Can someone please help with this? Greatly appreciated! 

[Qiu · Accepted solution]

@Emmm 
Here is my try. 
I should have added more details but I am on a rush for something else. Sorry.

[Emmm]

Thank you so much!!! @Qiu