How to stop formula happening until corresponding date in another column passes?

I am setting up a budget and daily spend calculator but am having trouble because my calculations for money not spent from a daily budget includes days that haven’t passed yet and therefore money is put into a “saved” box that isn’t really saved because it is budgeted for another day in the future.

Is there a way i can stop a formula in column C from happening until the corresponding date in column A has passed?

I have included a couple of screenshots to help demonstrate what I’m talking about.

Any help to fix this is greatly appreciated.

Paste in D3: =IF(NOW()<A3;"";D2+B3). Copy downward dragging the fill handle or with Ctrl+C, select, Ctrl+V.

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