Question on IF(AND or perhaps IF(OR in formula

I am stymied in my attempt to develop a formula that would check for the contents of a cell and if the cell is blank, fill in the cell with the value of the cell below, if that cell below is empty, continue checking until it finds a value and then fill in all empty cells (up to a cell that originally contained data) with that value.

I've attached my work thus far, the area I am working are all on the Summary tab, columns AA, AB and AC. For example, I'd like to put a formula in AA3 to AA16 that would result in the value 611.500. Like wise, I'd like a formula in cell AB18 that would result in 309.800, a formula in cell AB16 that would result in 306.5000 and a formula in cells AB3:AB14 that result in 305.000

I suspect that a IF(AND or a IF(OR formula might work, perhaps a formula that uses an array but I do not know how - would appreciate any and all help.

Thanks,
Tom