Dear Simha,
The Product ID label is filled on WDDOMODIFYVIEW on line
* Refresh
wd_this->mo_dodm_sc_i_bd->/sapsrm/if_cll_mapper~refresh( ).
If you go to class /SAPSRM/CL_CH_WD_DODM_SC_I_BD method /SAPSRM/IF_CLL_MAPPER~REFRESH you will see a line of code with comment
* Set label of input field ORDERED_PROD according to Material / Service.
There is where SAP sets the label you’re looking for.
Here you have 2 options: Make an enhancement to method Refresh or make an enhancement on method WDDOMODIFYVIEW and change the context attribute value for V_DODC_SC_I_BD.ORDERED_PROD_LABEL.
I hope it helps,
Regards