Interpolate data

Hi, I'm using the formulas below to interpolate a list of missing numbers. And then copy the formula in column A down to the next number.
Question is: is there a way to automate this using VBA or just formulas? The aim is to just having to enter the known numbers in the column
and then run a macro to fill in the rest.

A1: 9 B1: =(A7-A1)/(ROW(A7)-ROW(A1))
A2: =A1+$B$1
A3:
A4:
A5:
A6:
A7: 11 B7: =(A13-A7)/(ROW(A13)-ROW(A7))
A9: =A7+$B$7
A10:
A11:
A12:
A13: 27