I am trying to tell my cell to pull data from another worksheet from column A based on the first empty cell in column B.

A B
28,000 Done During Previous Contract
30,000 Billable to the Customer
SP30K Not Done
32,000 33,119
34,000 Not on Inv
36,000 37,018
38,000
40,000

My Desired result is 38000, however once the cell in column B next to 38000 is filled in my desired result would be 40000, etc.
This is the closest I go but it not working correctly...
{=INDEX(B3:B24,MATCH(TRUE,C3:C24="",0))}
I am looking for and excel formula not a macro. Thanks!