Use a field with a drop down to select the message template. Then setup the Message field to either lookup the template text from a related table (linked by your drop down field) or to use an auto-entered calculation to enter the template text specified by the drop down field.
Either way the template text can then be edited by you to customize the message body as needed.
Such an Auto-entered calculation can even include date from the current or related records to help personnalize the message before you even start to edit it.
how would i do this,
setup the Message field to either lookup the template text from a related table (linked by your drop down field) or to use an auto-entered calculation to enter the template text specified by the drop down field.
Simplest and most flexible is store the templates in a related table:
Define a table where each template is present in a text field, in separate records. Use a Second "template title" field to identify each template record.
Define a relationship:
YourEmailTable::TemplateType = EmailTemplates::TemplateTitle
Set your message text field up with the Looked up value field option to look up the template text from EmailTemplates.
Put YourEmailTable::TemplateType on your layout and format it with a value list of possible Template Titles. When you select a template, it will automatically appear in your message field and you can then edit the template to customize it.
If you want to include data from the current record or records related to it, you can use the calculation option instead of the Looked up value option.
If, for example, your template includes this text: Dear <SALUTATION>,
The auto-enter calculation can use this expression:
Substitute ( EmailTemplates::Message ; "<SALUTATION>" ; YourEmailTable::Salutation )
to replace <SALUTATION> to produce something like: Dear Mr. Smith,
(If you look up Subsitute in FileMaker help, you'll see there's a way to use  to make multiple subsitutions of different tags in a single use of the funciton.)
The result you get is customized text that you can still edit to customize even further if necessary.
the email table im using is called remiders
i made another table called email templates
reminders and email templates are in relatioship with message
im still not getting this
thanks for all the help
Why do you have four fields labeled "Template1, Template2, .... Template4" ?
You need just one field in place of these four to uniquely identify each message template which is stored in the message field of separate records for each template.
ok i have it working somewhat,
tmplatenumber is related to message field
i select whatever number an it work it gives me the proper template.
but it keeps creating records in the template table ( is it suposed to)
also if i select the wrong template number i then cannot change it i have to create a whole new record.
It sounds like you have added the message field from the template table instead of the message field defined in your email table that looks up the text in the message field of the template table. And I think you've clicked the "allow creation of records via this relationship" option when you shouldn't also.