How to make Time Not Change when working with sheet

Hello everyone. I've created a delivery sheet to keep track of the Invoice No. Customer Name and time of delivery. I am having problems to solve the NOW() function. I first used this function and I thought it was great until I noticed that the time always changed to current time every time I used the work sheet which was every 10 to 15 minutes. Here is the formula I put together which is good if you want the current time =IF(A10=1,NOW(),"") HOWEVER what I need is when I type in " 1 " in A10 I want to show the current time in H10 but to hold that time and not change. Is this possible, any help would be great. Thank you all for now Carlo.

Thank you for your help. Is there any command line can use to hold the time so it does not change.