Creating a calculated Bucket for stacked bar chart

[#1]

Hi

I am  a bit of a newby to Qlikview and think I have biten off more than I can chew.

I have a table

Department	Student	Enrolled	Course	retained
Dept1	STU1	1	Course 1	1
Dept2	STU2	1	Course 2	0
Dept1	STU3	1	Course 1	0
Dept1	STU4	1	Course 3	1
Dept3	STU5	1	Course 4	1

etc, etc

where 1 = retained and 0 - not retained

what I want to do is create create buckets of the % retained for each course ie =Sum (retained)/Sum (Enrolled)

so I had say, 1 bucket for courses retaining over 50%, over 75% and 0ver 90%

Everything I have tried so far has failed spectacularly, so won't embarrass myself by showing my workings.  I have looked through some previous discussions and can see how to create a bucet in the load script but cant figure out how to populate it with calculations

any help anyone could provide would be hugely appreciated

thanks

[#2]

For info

So far I have created the following table

RetentionGp:

load * INLINE

[RetNR, RetainedGP

1, <60

2, 60-69

3, 70-79

4, 80-89

5, 90+

];

then loaded the main data table

then created the following resident load

retainedPercents:

LOAD

    Course,

    Sum (retained)/Sum ([Enrolled]) AS PecentRetained

RESIDENT BaseData

Group by [Course];

now I want to put my courses into buckets based on % retained using

retainedBucket:

load  [Course code],

    PecentRetained,

    if(PecentRetained<=59,1,

    (if(PecentRetained<=69,2,

    (if(PecentRetained<=79,3,

    (if(PecentRetained<=89,4,5)))))))as RetNR

From retainedPercents

this is where I am coming unstuck (system error -

The system cannot find the file specified.)

which is understandable but i can't think how I can reference a 'resident load' table

I also feel i am making this this a bit more long winded than need be

again, any help would be most appreciated (and maybe in about 10 years I can start to return the favour)