You can add preconditions to your tasks. A task that does not satisfy its precondition will be skipped.
task default -depends A, B, C
task A {
  "TaskA"
}
task B -precondition { $false } {
  "TaskB"
}
task C -precondition { $true } {
  "TaskC"
}
Here task A and C will run, but not B.