Here is one way:
Code:
Sub StyleCheck_ContractionsTest()
Dim oRng As Range
Set oRng = ActiveDocument.Range
Selection.HomeKey Unit:=wdStory
With oRng.Find
.Text = "can't"
.MatchCase = False
.Wrap = wdFindStop
While .Execute
oRng.Select
If MsgBox("Do you want to amend the selected contraction?", vbYesNo, "Conver") = vbYes Then
If oRng.Characters.First = "C" Then
oRng.Text = "Cannot"
Else
oRng.Text = "cannot"
End If
oRng.Collapse wdCollapseEnd
End If
Wend
End With
MsgBox ("Complete!")
lbl_Exit:
Exit Sub
End Sub