Simple Mail Merge

Question

I'm still very new to c# and my programing skills are still basic.
I want to specify a start number in textBox1 and specify an end number in textBox2.
I have a .docx document which has set out spaces for label mail merge with 154 labels per sheet.
I want to click button1 to open the .docx document (named testMerge.docx and located in C:\) and have it populated with the start number e.g. 1001 and then the nextRecord should be 1002 and so on untill a maximum amount of labels had numbers on them before it went onto another page.

I have searched for hours and haven't found any simple code that i can understand.

Can someone show me how this can be done.

Many thanks.