I have a UDF (created by others) Tri_Wave(t, V1, V2, T1, T2) which is coded as such in VBA but is keyed into the spreadsheet cell as: =@Tri_Wave((A16;$H$8;$H$9$H$10;$H$11). The function works correctly but I don't understand why the VBA coding differs from the UDF typed into the cell. Why is there a @ in front of the UDF when typed into the spreadsheet cell?
Thank you in anticipation. 
Hi David,
Your answer is here: https://support.microsoft.com/en-us/office/implicit-intersection-operator-ce3be07b-0101-4450-a24e-c1c999be2b34?ui=en-us&rs=en-us&ad=us
| =MYUDF() | =@MYUDF() |
Implicit intersection could occur. User Defined Functions can return arrays. When they do, the original formula would have triggered implicit intersection. |
I suggest changing your function declaration, as it is now returns a Variant type, while it seems to be a decimal number:
Function Tri_Wave(t, V1, V1, T1, T2) as Double
