Hello Sudhan,
You can perform following steps:
1) Create new event message parameter field
2) Assign search help ZTIME_ZONE to this new event message parameter
3) Create custom implementation of BADI /SAPTRX/IF_BADI_WDA_UI
4) Change method BEFORE_EVM_BADI to read parameter from TRACKPARAMETERS and then update values of the parameters to TRACKINGHEADER-EVTTST based on event counter
5) Delete message paramter from TRACKPARAMETERS as it is not needed
Make sure that whatever time zone you have selected in your parameter is valid in TTZZ table.
Hope this will help. Let me know if you need additional information from my side.
Thanks,
Kinjal Rathod