Invalid Type

I'm very much new to VB.net arena
following function gives me trouble

:mad:

Public Function GetBalHrs() As Double
Try
Dim objConn As New System.Data.SqlClient.SqlConnection(sConnection)
Dim objReader As System.Data.SqlClient.SqlDataReader
Dim strSql As String
'strSql = "Select Sum(Hrs) as hrs From Project Where [Update] = 0 "
strSql = "Select Programme From Project Where [Update] = 0 "
Dim objcmd As New System.Data.SqlClient.SqlCommand()
objConn.Open()
objcmd.CommandText = strSql
objcmd.Connection = objConn
objReader = objcmd.ExecuteReader()
objReader.Read()
' Dim a As String
Return objReader.GetFloat(0)
' Return a
Catch myException As System.Exception
MessageBox.Show(myException.Message)

End Try
End Function

Hrs field type is Float
it says invalidTypecast
How can I solve this

Thankx in advance