How to check if an item in a table is between two times M:N - sql

Question

I have a many to many relationship between two entities. Computer and Booking, with the link entity being BookingToComputer which contains bookingID and computerID. Im trying to check that the computer is available for booking before adding it to the tables.
So I've selected the date, time, and hours of use (3 attributes in the booking table) of existing Booking records. I've created two time variable, start time (totalTime) and the end time of a booking (endtime). I've tried to put a loop to where each item in my list would go through all the selected rows from a datagridview to check if they match but I don't think I got it quite right and at this point im super confused.
Dim Part1 As String = txtTime.Text + ":00:00"
Dim Part2 As String = "00:" + txtTime1.Text + ":00"
Dim Part3 As String = "00:00:" + txtTime2.Text
Dim Time1 As TimeSpan = TimeSpan.Parse(Part1)
Dim Time2 As TimeSpan = TimeSpan.Parse(Part2)
Dim Time3 As TimeSpan = TimeSpan.Parse(Part3)
Dim TotalTime As TimeSpan = Time1 + Time2 + Time3
SQL.AddParam("#Time", txtTime.Text & ":" & txtTime1.Text & ":" & txtTime2.Text)
SQL.AddParam("#Date", txtDate.Text)
SQL.ExecQuery("SELECT bc.Computer_ID, hours_of_use, time_of_use FROM BookingToComputer AS bc, Computer AS c, Booking AS b
WHERE bc.Booking_ID = b.Booking_ID AND c.Computer_ID = bc.Computer_ID AND b.date_of_use = #Date AND b.time_of_use <= #Time;")
DataGridView2.DataSource = SQL.DBDT
If DataGridView2.Rows.Count() > 0 Then
'cell1 contains the hours used and time contains the time'
Dim TimeInt As Integer = DataGridView2.Rows(0).Cells(1).Value
Dim TimeInt2 As TimeSpan = DataGridView2.Rows(0).Cells(2).Value
Dim Addit As String = TimeInt.ToString + ":00:00"
Dim interv As TimeSpan = TimeSpan.Parse(Addit)
Dim endtime As TimeSpan = TimeInt2 + interv
Dim rowpass As Integer = 0
For Each x In listpick
Dim CompID As Integer = DataGridView2.Rows(rowpass).Cells(0).Value
If x = CompID Then
If endtime > TotalTime Then
MsgBox(x & " is already reserved.")
Else
MsgBox("diff time, same comp")
End If
Else
MsgBox("Good time - diff comp")
End If
rowpass = rowpass + 1
Next
End If