This will give you mark1=90 as result:
VB.Net Code:
  1. 'regex with 1 capture group: (.*)
  2.    Dim srgx As New System.Text.RegularExpressions.Regex("(.*)\sFor English3 & English2")
  3. 'text you need to parse
  4.    Dim tmpstring As String = "mark1=90 For English3 & English2"
  5. 'Find Capture Group in:
  6.    Dim matchG As System.Text.RegularExpressions.MatchCollection = srgx.Matches(tmpstring)
  7.    MsgBox(matchG(0).Groups(1).ToString())

If you had multiple different entry strings, let me know to make a little change to above code, but then I will need a few more samples...