Code to use a varible integer inside a formula in VBA

I am working on a workbook that has a summary sheet. The original workbook was created with 40 sheets that were linked back to the summary sheet. I have changed the workbook so there are only 5 sheets to start out with, but have created a macro to add an additional sheet if needed. This way there isnt a bunch of empty sheets when the project is finished. The problem I am having is with the summary sheet. All of the cells come up with a ref error because the sheet that the cell was originally linked to has been deleted. I need to create a macro that will adjust the cell to the name of the sheet that is created with the macro. I think this should be easy because the names of the sheets that are being added are just 6, 7, 8, and so on, so if I could figure out how use a varible integer inside a formula in vb i could loop it through the cells and get it to work, but Im having a heck of a time using these integers. Here is an example of the formula in vb i need.

Range("b15").Select
     ActiveCell.FormulaR1C1 = "='8'!R3C[18]"

I need the red 8 to be a variable integer such as "x" that would be based on the sheet count.

Thanks any help is appreciated