The Submit button has three Display Mode properties - disabled, edit and view.

Using an IF statement I check whether each field on the form has data or is blank. If one of the fields is blank then the Submit button is set to Disabled otherwise the Submit button is set to Edit allowing the user to submit the form data.

If(And(!IsBlank(dceLeaveFromDateValue),!IsBlank(dceLeaveToDateValue),!IsBlank(dceLeaveTypeValue),!IsBlank(dceMedicalCertificateValue),!IsBlank(dceReasonForAbsenceValue),!IsBlank(dcePayTypeValue)),DisplayMode.Edit,DisplayMode.Disabled)