are you allowed to use another char array to save the reversed string? If you are, then start at the end of the original string and work backwards towards the first character, in the loop store each character in the second array from front to last.
For example, if the string is "abc" then start with the last character which is 'c', copy it to the first byte of another string.
There are several ways to accomplish that, but the simplest is probably calling strlen() to get the length of the original string, then a for loop to count from whatever that returns to 0.
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...