As said you will a Timer control on your form and perhaps DateTimePicker (can be found in MS Windows Common Controls 2 6.0).
So, add those to your form as well as textbox and copy/paste/run this sample code:
Code:
Option Explicit
Dim myTime As String
Private Sub Form_Load()
Timer1.Enabled = False
Timer1.Interval = 1000 '1 second <<< 60000 = 1 minute
DTPicker1.Format = dtpTime
DTPicker1.Value = Now
End Sub
Private Sub Command1_Click()
myTime = DTPicker1.Value
Timer1.Enabled = True
End Sub
Private Sub DTPicker1_Change()
If DTPicker1.Value < Now Then DTPicker1.Value = Now
End Sub
Private Sub Timer1_Timer()
If CDate(myTime) = Now Then
MsgBox Text1.Text
'you may need to call some function here
Timer1.Enabled = False
End If
End Sub