It would be much easier to help you with an example if you provide more details...
First, which cell or cells?
What is the condition which brings about the flashing?
What color will the text flash? As is?
Do you want the cell's interior to flash instead, as well, or not at all?
What condition or user action will stop the flashing?
Will any other VBA procedures need processor time to run at the same time as the procedure which flashes your text?
This question has been raised here before. Have you made a decent effort to search previous posts?