The following code works assuming you have a connection to he database or datasource:
You first need to declare your Crystal objects as follows
Dim lReportApp As CRAXDDRT.Application
Dim lReportDatabase As CRAXDDRT.Database
Dim lReportTables As CRAXDDRT.DatabaseTables
Then set your Crystal objcts
Set lReportApp = New CRAXDDRT.Application
'strReportLocation is a variable representing where the report is, you could hard code the path of the actual report
Set lrptReport = lReportApp.OpenReport(strReportLocation)
Set lReportDatabase = lrptReport.Database
Set lReportTables = lReportDatabase.Tables
Then set your report viewer equal to your data source which could be a strsql statement, the results of a function, a table in a database, etc
lReportTables = strSql
crviewer.reportsource = lReportTables