Sub form not show by button

Sir ji
Namaskar

I have created a sub form which is made to press yes/no with a button in the purchase voucher.

This form appears after selecting the item.
This is working fine in prime but in erp9,
as soon as the button is pressed,
the cursor appears in the reference field.

Why is this happening ?
I am unable to understand this.

Please help sir.........

code attached.

Code:

[Report: Voucher]
    Variable:dthform

[#form :purchase color]
    add:button:xyz23

[Button:xyz23]
  
    Title:  if ##dthform then $$LocaleString:" No" else $$LocaleString:" Yes"
    Key: alt + 8
    Action  : Set : dthform : NOT ##dthform
  
[Variable:dthform]
  
    Type        : Logical
    Volatile    : No

[System:Variable]
    dthform:""

[#Field: VCHACC StockItem]

    ;Switch:case1:hkpurc23:not ##dthform

    option:hkpurc23:not ##dthform
  [!field:hkpurc23]
    add:Sub Form : Before  : STKVCH BatchAllocations     : hksformnew


[Report: hksformnew]
    Form:hksformnew
    [Form:hksformnew]
        Part:hksformnew
        Height:20% screen
        Width:20% screen
        [Part:hksformnew]
            Line:hksformnew
            [Line:hksformnew]
                Field:name field
                Local:Field:name field:Set as:" Welcome to the world of TDL"

 

Sir
Video attached in zip file