Thanks for the query.
IUI will be done when the larger follicle ruptures.
And usually one only follicle releases in one cycle.
So one IUI around 36 hours after giving HCG injection
If your doctor suggests you can go for repeat IUI on the same day evening or next day morning. Usually all these will be done for the first larger follicle only.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429