how to put a value to a control in Crystal report

Create one formula field.

For Example @UserDefineValue

Now assign formula field to any control which you want to display value.

At run time you can use following line in your code.

dim sr as string.
' and I assign a value to this variable
sr="Admin"

dim objReport as New Report1
objReport.DataDefinition.FormulaFields("@UserDefineValue").Text = sr

That's it.