time delay in simple program

Hi,

i have a little time problem. i've wrote a program which creates in an area a specific numbers of rectangles ... so it begins in the left buttom corner, creates rectangles on the buttom to the right until the end of the area(with a while loop). after this, with an other while loop i jump up one line. in this line the first while loop makes his work again. and so on until the area is full of rectangles.
so this works in principle. but when the procedure jump in the second line it starts to become extremly slowley. and it doesn't matter how many rectangles are created.

so i can't understand why it becomes so slowely when the program starts the same procedure for a second time.

regards
Philip

p.s.: this is only a short extract out of my program. so in the same time where a rectangle will be created, it creates a new cellview which will be opened an closed again.