excel Vba

I have a program issue number eg 10.0009 which i update after any program changes it is incremented by 0.0001 however when implemented the new issue number 10.001 instead 0f 10.0010

Dim iOldId, sNewId
Dim iNewId, OldId As Double
iOldId = ActiveSheet.Cells(4, 11).Value
iNewId = iOldId + 0.0001

I wonder if anyone could please point me in the right direction