Try This...
Dim pmtDiscValue As New ParameterDiscreteValue
pmtDiscValue.Value = txtMinValue.text
cryRpt.ParameterFields("FromNumber").CurrentValues.Add(pmtDiscValue)
pmtDiscValue.Value = txtMaxValue.text
cryRpt.ParameterFields("ToNumber").CurrentValues.Add(pmtDiscValue)
Let me know if you have any question related this post.