Forms Data Controls :: Comparing Dates From Two Different Tables?

I have two tables along with some of its attributes as follows:

ProjDetails: ProjID, StartDate, EndDate
ActDetails: ActID, AStartDate, AEndDate,

What i would like to do is to compare the AStartDate with both StartDate and EndDate which will be done in a DetailsView both insert and edit mode. This is to make sure AStartDate is within both those dates. (Same goes for AEndDate)

At first i though of extracting the StartDate and EndDate from the database and then make the comparison. But i am having problem because both StartDate and EndDate are data type "date" as follows:

Dim strProjDate As String

Using myConn3 As New SqlConnection(connString)
myConn3.Open()
Dim command3 As SqlCommand = myConn3.CreateCommand()
command3.Connection = myConn3
command3.CommandText = "SELECT StartDate FROM ProjDetails WHERE ProjID = @ProjID"
With command3.Parameters
.Add(New SqlParameter("@ProjID", TB_GenerateActID.Text))
End With
strProjDate = command3.ExecuteNonQuery()
TB_ProjStartDate.Text = strProjDate.ToString
End Using

The above code only displays "-7" in the TB_ProjStartDate textbox.

By the way, I am using Web Developer 2008, VB.net.