extracting a part of a number from one cell to another

I am doing a study on almost 2000 patients in OSLO, Norway. In the excel fil i received to work with Column A has the patient's birth dates registered in cells as 5 or 6 digit numbers, in a dmmyy og ddmmyy format depending if the day is above the 9th of a month or not (F.eks: 11176 would be November 1st 1976, 110176 would be January 11th 1976). I need to extract the birth month and year into columns B and C. This would take forever doing it manually and i wonder if there is a function that i can copy into each cell that will automatically extract the information out of column A.

row nr.-----A(dmmyy/ddmmyy)-----B (Month)-------C(Year)
--1--------------90511----------------05------------11
--2-------------151263----------------12------------63
--3--------------21255---------------code?---------code?
--4-------------200220-------------copy code----copy code

Im do know simple formulas for excel, but i dont have any idea how to do this. Does anyone have any ideas for what to put as a formula in column B and C? Help much appreciated!!