Insert cell with text within cell that has large amount of text(non formula)

I have a cell that has a large amount of text in a non formula. One of the statements i trying to modify to reference another cell that has text, that adjusts based on other conditions. here is an example:

Test Header

this is letting you know you have (xx months) to make a choice on the issue
by not doing it, you could have some issues in the future regarding the matter
please response, some more addition text

Do you understand?

since it is not in a formula format, it is making it harder to have/replace part of the text. What i am trying to do is to have the (xx months) replaced with a cell reference within the text of the cell that is not in a formula format, so (xx months) = "&Sheet1!A1&" which in other conditions is and has worked fine, but not sure on a cell that has text in a non formual format. Is this even possible? I have tried to break apart each line to individual cells, which works with the char(10) between each line if both a = or concatenate forumual, however it removed formating of the text (ie bold/underline, etc)