Array Search Function Problem

The purpose of the following Function is to search the 25x1 array A$ (with a 0 in the second array dimension) for the entry specified in on$, and return a 1 if it is there, and a 0 if it isnt

Function SearchAnims(on$)
While Not (TNum = 26 And oncheck$ = on$)
oncheck$ = A$(TNum, 0)
TNum = TNum + 1
Wend
If TNum = 26 Then
Return 0
Else
Return 1
EndIf
End Function

The function doesnt do that however, it used to return a 0 weather the entry was present or not until I added the $ signs to on$ and oncheck$, now it complains about the array element being out of bounds

Any help would be much apreciated