How to modify table data while loading?

[#1]

Hi,

I have a table as described below:

IM     RUN     

1234     20     

1234-10     0     <== IM changed as it's less than the previous one

1234     11     

1234     23     

1234     40     

1234-14     7     <== IMchanged as it's less than the previous one

1234     12     

1234     30     

Now what I need to do is to change all the occurences of IM till RUN is again less than the previous RUN:

IMEI     RUN

1234     20

1234-10     0

1234-10     11

1234-10     23

1234-10     40

1234-14     7

1234-14     12

1234-14     30

I tried to use loop but it didn't work properly, can anyone help with this?