Copy cell above in formula

Question

I have created this formula:

=IF([is Child]@row = "T", [Estimate Number (1)]1814, VALUE([Estimate #]@row))

I am trying to copy the estimate number from the row above if the current row is a child. Works fine until the sheet is sorted. How do I change this formula parameter "[Estimate Number (1)]1814" to copy the cell above no matter what the row number.

I was trying something like "[Estimate Number (1)]@row-1", with no luck.

Is this possible?

Thanks