You did not provide enough information about your issue, especially about the reason of that behaviour. You did not provide your code too. Well, we can only guess...
First of all, i'd suggest to read about Using early binding and late binding in Automation
], Early and Late Binding (Visual Basic)
Once you are using:
Set xlApp = Excel.Application
Set xlBook = GetObject("file.xls")
You need to decide which binding method do you want to use.
Secondly, you need to use Excel's object and methods:
Dim xlApp As Object
Dim xlWbk AS Object
Dim xlWsh AS Object
Set xlApp = CreateObject("Excel.Application")
Set xlWbk = xlApp.Workbooks.Open("FullFileName.xls")
Set xlWsh = xlWbk.Worksheets("SheetName")
.Range("A1") = "Test"
.Range("C3") = 3
xlWsh = Nothing
xlWbk = Nothing
xlApp = Nothing
Thirdly, there are known issues with MS Office 2010/2013:
Compatibility issues in Office 2013
VB6 based add-ins may fail to work in Office 2013
Finally, please refer this:
Essential Training for Visual Basic 6 Developers
By The Way: I'd like to say: who wants to use VB6, when VB.NET is more powerful, efficient, etc.?