Variable COUNTBLANK??

[Riddlemethis]

So I've a column AA with a load of helper cells in it with equals to "1" indicating the start of a new 'workload' however the type of workload is dictated by the number of gaps in the column until the next 1.
I need a way to use maybe COUNTBLANK or other method but only to sum the number of blanks until the next 1 and return the value in the next column. The '1' is always in a variable cell depending on the data that is inserted that day which is where I'm struggling. Is this possible?
Image attached has blank count manually typed in AB for an example of what I'm looking.

 

[Fluff]

How about

Fluff.xlsm
	AA	AB
1
2	1	4
3
4
5
6
7	1	2
8
9
10	1	4
11
12
13
14
15	1	4
16
17
18
19
20	1	?
21
22
23
24
Main

Cell Formulas
Range	Formula
AB2:AB20	AB2	=IF(AA2="","",IFNA(MATCH(1,AA3:AA100,0)-1,"?"))

 

[Riddlemethis]

How about

Fluff.xlsm
	AA	AB
1
2	1	4
3
4
5
6
7	1	2
8
9
10	1	4
11
12
13
14
15	1	4
16
17
18
19
20	1	?
21
22
23
24
Main

Cell Formulas
Range	Formula
AB2:AB20	AB2	=IF(AA2="","",IFNA(MATCH(1,AA3:AA100,0)-1,"?"))

Yes Fluff! Works perfectly. Thanks for your help.

 

[Fluff]

You're welcome & thanks for the feedback.