Return The Date In The Cell Containing The Formula

the last date input into a range covering multiple columns and return the date in the cell containing the formula):

{=index(a9:n9,1,max(if(cell("format",a9:n9)="D4",column(a9:n9)))-column(a9)+1)}

My column headings use this pattern:

Column A: Date
Column B: Amount
Column C: Date
Column D: Amount
Column E: Date
Column F: Amount

and so on.

When I use the above formula, I end up with data from the last amount column instead of the last date column.