help needed in group wise discount

sir

I want to provide group-wise discount on total quantity at voucher, I have written this code
please help in correction


;;==================At Voucher================================

[#Line : EI Column One]
Add : Right Field: At Beginning: GRPName

[Field: GRPName]
Use:Name Field
Set as: "Group Name"
Skip: Yes
Width:10
Align: Center

[#Line : EI Inv Info]
Add: Right Field:At Beginning: GRPNameNo

[Field: GRPNameNo]
Use: Name Field
Set as:$PARENT:STOCKITEM:#VCHSTOCKITEM
Width:10
Align: Center
Skip:Yes


;;====================logical Above Narration =============================

[#Part: VCH Narration]
Add: Line: at end: GWD Logical

[Line:GWD Logical]
Fields : Medium Prompt, GWD Logical
Local : Field : Medium Prompt : Info : $$LocaleString:"Provide Group Wise Discount ?"
Space Top : 0.4

[Field:GWD Logical]
Type:Logical
max: 3
Width:3
Style: normal Bold
Table: Yes No Table
Show Table: Always
Storage: GWDLogical
Sub Form: GWDisc : $$Value= "Yes"

[System:UDF]
GWDLogical:Logical: 930

;;========================== Main Report =============================================

[Report:GWDisc]
Form:GWDisc

[Form:GWDisc]
Part:GWDisc

[Part:GWDisc]
Line:GWDTitle, GWDisc
Repeat:GWDisc:GWDColl
Total:GWDAmt
Bottom Line:GWD Total
Break On:$$IsEmpty:#GWDAmt
Scroll:Vertical
Common Border:Yes


[Line:GWDTitle]
Field:GWDName, GWDQty, GWDRate,
Right Field:GWDAmt
Local:Field:GWDName:Info:"Group Name"
Local:Field:GWDQty:Info:"Group Total Qty"
Local:Field:GWDRate:Info:"Discount Rate"
Local:Field:GWDAmt:Info:"Discount Amount"
Border:Column Titles

[Line:GWDisc]
Field:GWDName, GWDQty, GWDRate,
Right Field: GWDAmt

[Field:GWDName]
Use:Name Field
Set as:$parent
Storage:GWDName
Width:25
Skip:Yes

[Field:GWDQty]
Use:number Field
Set as:$BilledQty
Storage:GWDQty
Width:20

[Field:GWDRate]
Use:number field
Set as:$rate
Storage:GWDRate
Width:20

[Field:GWDAmt]
Use:number Field
Set as: #GWDQty * #GWDRate
Storage:GWDAmt
Width:20
Set Always:Yes

[Line:GWDTOTAL]
Right Field:GWDT Title, GWD Total

[Field:gwdttitle]
Use:medium prompt
Info:"Total discount amount :"
Skip:Yes

[Field:GWD total]
Use:Number foeld
Set as:$$Total:GWDAmt
Storage:GWDTotal

[System:UDF]
;gwdtotal:Aggregate: 931

;;===================== Storage =====================================

[System:UDF]
GWDValue:Aggregate:101
GWDName:String:102
GWDQty:Number:103
GWDRate:Number:104
GWDAmt:Number:105

;;==================== Collection ==================================

[Collection:GWDColl]
Source Collectionefault
Walk:Inventory Entries

By:stockitemName:$stockitemName
By:$parent:$Parent;:Stockitem:$stockItem
;By:rate:$rate

Aggr Compute:BilledQty:Sum:$BilledQty

 

CAN ANYONE HELP IN THIS???????