Integration Services :: SSIS Package With Webservice As Destination

I have a table is SQL server database A that is my source. I have another database B which is accessed via webservice call.(its a CRM server basically). My intention is to transfer data from A to B while B is accessible only via web service. I need to update existing one and create the missing one.

Currently I am using script component, and on every insertion of a row, i call the webservice to check if the record exist or not. If it exist I update it else create it using webservice call itself.

All this happen in Input0_ProcessInputRow(Input0Buffer Row) function.

Now this method is making 2n webserive call which is making the performance very slow.
 
I want to optimize the approach. Is there a way where I can retrieve whole set of rows in source table in preexecute(), filter it and store it in a List. This way, i just need to check the list a perform update ro create accordingly preventing my webservice call.

How to optimize this or even some better approach?

Its actually a CRM server and I am trying to update and create contacts in CRM sync with a database.