can't drill down to voucher alteration

Dear All TDL Experts,

I have written following code

[Field : MyvchDate]
Use : short Date Field
Set as : $Date
Alter : Voucher

When I enter the Field , It does not show the voucher in Alteration Mode.


But "Display : voucher" is working, It shows the voucher correctly only in display mode.

Please let me know the reason, please help me.

 

Dear Admin Sir,
Thanks lot for your immediate reply, I tried as per your valuable suggestion. But i can't achieve the result. Here I attach my code. Kindly please help to solve.
[#Menu : Gatewayoftally]
Item : My voucher Report : Display : MyvchReport

[Report : MyvchReport]
Form : myvchform
Title : $$LocaleString:"Sales Vouchers"
Family : $$Translate:"Sales Vouchers"
Use : DSP Template

[Form: Myvchform]
Height : 100% Page
Width : 100% Page
Part : Myvchtitle,MyvchBody
Bottom Part : myvchbotomtot
Use : DSP Template

[Part : Myvchtitle]
Line : Myvchtitle

[Line : Myvchtitle]
Use : MyvchBody

Local : Field : Default : Type: String
Local : Field : Default : Align : center
Local : Field : Default : Style : Normal Bold
Local : Field : myvchdate : set As :"Date"
Local : Field : MyvchptyName : set As : "Party Name"
Local : Field : myvchNumber : set As : "Vch.No."
Local : Field : Myvchtype : set As : "Vch.Type"
Local : Field : myvchamt : set As : "Amount"
Border : column Titles

[Part : MyvchBody]
Line : MyvchBody
Repeat:MyvchBody:myvchcoll
Scroll : Vertical

[Line : myvchbody]
Field : myvchdate, MyvchptyName, myvchNumber, Myvchtype
Right Field : myvchamt
Option : Alter on Enter
Local : Field : Default : Style : Normal


[Field : myvchdate]
Use : Short Date Field
Set As :$Date

[Field : MyvchptyName]
Use : Name Field
set As :$PartyLedgerName
Width : 40% Page
space Left : 5% Page

[Field : myvchNumber]
Width : 10% Page
set As :$VoucherNumber
Align :center

[Field :Myvchtype]
Width : 20% Page
set As : $voucherTypeName
Align : center

[Field: myvchamt]
Use : Amount Field
Set As :$Amount

[Part : myvchbotomtot]
Line : myvchbotomtot

[Line : myvchbotomtot]
Use : MyvchBody

Local : Field : Default : Type: String
Local : Field : Default : Align : center
Local : Field : myvchdate : set As :""
Local : Field : MyvchptyName : set As : ""
Local : Field : myvchNumber : set As : ""
Local : Field : Myvchtype : set As : "Total"
Local : Field : myvchamt : set As : $$collamttotal:myvchcoll:$Amount
Local : Field : myvchamt :Type :Amount
Local : Field : myvchamt :Align:Right
Local : Field : Default : Style : Normal Bold
Border : Flush Totals
[collection : myvchcoll]
Type : vouchers : vouchertype
child of : $$vchtypesales
belongs to : yes
Fetch : Date, PartyledgerName, VoucherNumber,vouchertypeName, Amount