During pass value in crystal report through textbox

Error : Subscripition Out of range

I want to pass the text value in field...bill_amt of crystal report
report1.rpt is crystal report

for this i used-----
Dim APPL As CRAXDRT.Application
Dim rpt As New CRAXDRT.Report

Set APPL = New CRAXDRT.Application

x = App.Path & "\" & "report1.rpt"
Set rpt = APPL.OpenReport(x, 1)
rpt.DiscardSavedData
rpt.Database.SetDataSource RS
rpt.ParameterFields(bill_amt).Value = Text5.Text 'subscript out of range

'cryst is crystal report
Cryst.ReportSource = rpt
Cryst.ViewReport

how this problem resolved???