ABAP: 'DYNP_VALUES_UPDATE' is not working for VA01/VA02

Dear ABAP Experts,

I am trying to update value of KWMENG (Quantity Field in va01 / va02 ) by using the function DYNP_VALUES_UPDATE in the include MV45AOZZ but unable to see the changed value. I am using the following code.

DATA: dynpfields1 LIKE dynpread OCCURS 5 WITH HEADER LINE.

DATA: l_stepl LIKE sy-stepl.

REFRESH dynpfields1.

CLEAR dynpfields1.

dynpfields1-fieldname = 'RV45A-KWMENG'.

"Screen field name dynpfields1-fieldvalue = count1.

CONDENSE dynpfields1-fieldvalue.

dynpfields1-stepl = 1.

APPEND dynpfields1.

CALL FUNCTION 'DYNP_VALUES_UPDATE'

EXPORTING dyname = 'SAPMV45A'

dynumb = '4001'

TABLES dynpfields = dynpfields1[]

EXCEPTIONS OTHERS = 0.

What can be the reason ? Any idea about this.?

Regads

Aneel