to measure a section you can use
/** Makes a montage jump to a named section. */
UFUNCTION(BlueprintCallable, Category="Animation")
void Montage_JumpToSection(FName SectionName);
/** Makes a montage jump to the end of a named section. */
UFUNCTION(BlueprintCallable, Category="Animation")
void Montage_JumpToSectionsEnd(FName SectionName);
and the function
/** Get Current Montage Position */
float Montage_GetPosition(UAnimMontage* Montage);
and subtract
Rama