vb.net save image with text box name

I'm not a VBA person at all but can anyone please let me know how to save an image with the image name being the textbox field which is entered on the form?
Current code below saves image as eSig.bmp
the textbox name is jobnumber.

cheers for any help.

Private Sub btnSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSave.Click
Try
If (sc.SignatureCaptured = True) Then
btnSave.Enabled = False
System.IO.File.Delete("\My Documents\eSig.bmp")
sc.Save("\My Documents\eSig.bmp")
sc.Clear()
Else
MessageBox.Show("No signature has been captured")
End If
Catch ex As Exception
MessageBox.Show(ex.Message)
Finally
btnSave.Enabled = True
End Try
End Sub