Filling blank values in a non-linear series with linear values with a formula

I am trying to fill in some null values in my data with a linear step between 2 known values. In the example between row 5 and 10, there is 4 blank cells and a total difference of 2 (9-7), so each cell in that range would increase by .4 resulting in a linear step from 7 to 9. I can not figure out a formula to put into all the blank cells to generate values. I need a certified genius on this one lol

Current Data Set:
3
4

6
7




9





23




45




67


Answer Set:
3
4
5
6
7
7.4
7.8
8.2
8.6
9
11.33333333
13.66666667
16
18.33333333
20.66666667
23
27.4
31.8
36.2
40.6
45
49.4
53.8
58.2
62.6
67

Hi Hendo, try this into B2 and copy down:

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Edit:- Asked unnecessary questions plus a typo.
Edit Again: Actually, one question was relevant, as my formula will only work if numbers are in sequential order like in your sample.

Please try at B2
=IF(A2,A2,B1+(INDEX(A3:A$28,MATCH(1,INDEX(--(A3:A26<>""),),))-LOOKUP(9^9,A$1:A1))/(MATCH(1,INDEX(--(A3:A$28<>""),),)+ROW()-MATCH(9^9,A$1:A1)))