[Elsemeravin]

I just also tried that, but the Tech B is grayed out and never change:

Name := A
Group := CG_General Topic
Description := Tech A.
Picture Number := 32
Maximum Level := 10
Level Cost := 50000
Start Level := 0
Can Be Removed := True
Unique or Racial Tech := False
Number Of Requirements := 0

Name := B
Group := CG_Specialization
Description := Tech B.
Picture Number := 104
Maximum Level := Get_Empire_Tech_Level("A") * 3
Level Cost := 10000
Start Level := 0
Can Be Removed := True
Unique or Racial Tech := False
Number Of Requirements := 1
Requirements Evaluation Availability := AND
Requirements Evaluation Allows Placement := TRUE
Requirements Evaluation Allows Usage := TRUE
Requirement 1 Description := Empire must have at least tech level 1 in A.
Requirement 1 Formula := Get_Empire_Tech_Level("A") >= 1