Yeah, you need to create an expression.
Its fairly easy tho.
Add a new parameter, call it something like 'strUpdateSQL'
change it to a string.
Make sure you Properties Pane is open (F4)
Click on the parameter value. No go to Properties pane, Change the evaluateasexpression property to True.
Click the Expression Elipses.
and your expression will be something like:
"UPDATE dbo.my_table SET SrcRecCnt = (select COUNT(*) from My_db.dbo.xyz)
WHERE BatchID=" + (DT_STR, 10, 1252) @[User::BatchID]
@[User::BatchID] is the Parameter you want to use for your batch ID.